Nozzle Dreams

Author: Dennis J LeGear, Capt. Ret. Oakland Fire, CA

Uncommon thoughts about commonly used suppression equipment: “The Missing Tip” and Optimum Handline Flow in 2 ½-inch Hose

(Part I) The Need to Address Maximum Deployable Handline Flow in 2 ½-inch Hose

There has been a flood of information over the last two decades in the fire service in regards to nozzles and flow rates.  This has mainly focused on initial flows in 1¾-inch attack handlines. The significance of flow rate has been overlooked in 2½-inch handlines.  Many interrelated factors indicate the need to address optimum 2½-inch handline flow rate. Several are: modern hydrocarbon fuel loads, rapid fire development, energy efficient building construction, reduced staffing, and longer fire development before initial extinguishment efforts. Taken together, these factors push the fire service to address the need to deliver more water through the initial attack handline. This situation begs the question, has a potentially very useful nozzle and flow rate been overlooked in the 2½-inch handline.  To simplify the discussion, smooth bore tips are used as template examples with an ideal nozzle pressure of 50 psi. The argument has been scientifically made and proven for water application in either a straight stream from a fog nozzle or, preferably, a solid stream,and that this represents today’s best practice for stream selection for structural fire extinguishment. The goal of this discussion is to address optimum flow rate. To be sidetracked into a debate regarding 30 degree fog vs. solid or straight stream would hinder this purpose. 

“A Quantitative Approach to Selecting Nozzle Flow Rate and Stream” parts one and two by Jason N. Vestal and Eric A. Bridge (Oct 2010,Jan 2011;Fire Engineering) illustrates just how many influences there are in nozzle/stream selection and flow rate.Vestal and Bridge cite National Fire Protection Association (NFPA)1710 recommendations that the sum of the flow of the first two handlines placed into operation at a structure fire be a minimum of 300 gpm,and that the first handline flow a minimum of100 gpm. They discuss,at length,several National Institute of Standards and Technology (NIST) studies regarding flashover research, heat release rate, and the heat absorbing capacity of streams. This article represents the most detail-oriented and exhaustive look at effective initial handline flows and stream selection that I know of to date. 

Vestal and Bridge also discuss nozzle reaction, stream quality, reach, penetration, type of stream, and unintentional reduction of gpm flow with an emphasis on kinks in the line.  Heavily touched upon is the ability of crews to effectively manage and deploy handlines, focusing on nozzle pressure and nozzle reaction. Vestal and Bridge also make a strong case, citing a litany of research and data, that most first-due urban engine companies are arriving at the time of greatest concern in fire development: slightly before, at, or just after flash over.  Reading both parts one and two is strongly recommended; for they represent a definitive scientific examination of what first arriving companies are facing today at most common residential structure fires.

Vestal and Bridge conclude that a minimum initial fire flow of 160 gpm is needed in 1 ¾-inch hose and based on kinks that reduce attained nozzle pressure on the fire ground they recommend a 15/16-inch smooth bore tip. This is a logical choice even though the 15/16-inch smooth bore tip is rated at 185 gpm at 50 psi, as a few kinks and or poor line management can reduce flow to around 160 gpm. Most of the discussion regarding handlines in the modern fire service has been centered on 1¾-inch hose because that is the size of line used most often.  Logically, if there has been such a need for greater flow in the 1¾-inch attack handline, one must also examine the flow rate of the 2½-inch attack handline. 

The two common smooth bore tip sizes used on 2½-inch attack handlines are 11/8-inch and 1¼-inch. Their respective flows at 50 psi nozzle pressure are 266 gpm and 328 gpm. For reasons stated below, this article shall propose the consideration of a 1 3/16-inch smooth bore tip, which provides a flow of essential 300 gpm at 50 psi.  (This flow and nozzle reaction could be achieved by a fog nozzle designed to flow 300 gpm at 50 psi).

In the author’s fire service career, three things have dictated the choice of initial attack handlines. If a handline could not properly suppress a fire, based on the below principles, then the engine company would start an aggressive master stream attack with the goal of moving towards an interior operation, if viable, after initial knock down. The three guiding principles in decision-making are as follows:

1)Critical flow rate. William E. Clark’s principle of “critical flow rate”, described as the minimum flow in gpm needed to extinguish a given fire,is discussed in detail in his book Firefighting Principles and Practices(34). One must make sure the handline will, at the minimum, meet the “critical flow rate”. Optimally, the actual flow rate will far exceed the “critical flow rate”. This will lead to rapid knock down, thereby having the most life saving and property conserving potential. He went on to say, “When a fire continues to burn after water has been applied, it is for one of two reasons. Either the water is not reaching the burning material, or it is not being applied at a sufficient flow rate”.

2)Hydraulics.  Is the handline pumped properly? Is the flow attainable with the length of the stretch and the size of the hose? Is there adequate reach and penetration?  David P. Fornell, in his Fire Stream Management Handbook,addresses these issues.

3)Deployability.  Once the two above criteria have been met,does the handline have a nozzle reaction manageable by a reasonable number of personnel?  Can it be advanced while flowing and maneuvered through a structure with inherit obstacles such as furniture, doors, staircases, etc. Fornell described, at length, the advantages of having the lowest possible nozzle reaction while still maintaining an effective stream.  Retired FDNY Chief Vincent Dunn also expressed the strong opinion that flows in excess of 300 gpm were of large caliber and considered master streams,in which mechanical aid should be provided to maintain adequate control and safety. (Dunn 102)

In this article the color scheme in most tables dictates that red highlighting represents negative consequences.The green highlights represent positive consequences. The yellow highlighting represents the limits of flow and nozzle reaction for handline operations. 

Below is Table #1. It includes five commonly used smooth bore tip sizes and the proposed 13/16-inch smooth bore tip. The two most commonly deployed smooth bore tips are the 7/8-inch tip and the 15/16-inch tip. Both are used on 1¾-inch attack handlines.  Both meet the NFPA 1710 recommendation of 300 gpm combined flow if two lines are pulled, pumped properly, and devoid of significant kinks.  Respectively, they produce flows of 161 gpm and 185 gpm at 50 psi nozzle pressure. Nozzle reaction and flow for the chart were calculated by the equations given at the bottom. In addition, those flows have been reproduced via flow test, plus or minus 5 gpm by hand-held pitot gauge.(Except in 13/16-inch smooth bore tip)

* Note the 40 to 60 psi spread in Table #1 for nozzle pressure. Vestal and Bridge in their article noted that fire ground flows based on pump pressure commonly did not produce the rated flow of nozzles, mainly due to kinks and poor line management.  This will be referred to as a soft nozzle (low pressure). This is usually due to human error. However, they did not discuss the opposite occurrence, the hot nozzle (high pressure). This is a condition that is at least as common as the soft nozzle. Chief David McGrail, Denver Fire Department (DFD), in his article, “Keys to Success with the Big Line”, brings out the specter of an over-pumped handline. Many factors can lead to a hot nozzle. Several are: rounding up on pump charts, securing a pressurized water source like a hydrant without throttling back, over estimating the dead load stretch, pumps that idle at a high pressure, errors in pressure gauges, relief valves and governors that have trouble maintaining pressures below 130 psi when a hydrant is secured, pump operators with the attitude that it is better to err toward more pressure rather than less, attempting to knock out minor kinks with pump pressure, pump operators not used to pumping large handlines with low friction loss requirements, low lighting, stressful conditions, and poor ability to gate lines down which leads to gate creep if no gate locking mechanism is provided.  Based on these facts a good pump operator will, at best, produce a nozzle pressure within a range of plus or minus 10 psi of the rated 50 psi nozzle pressure.  In departments the author has been involved with, both as an instructor and an operating member, a hot nozzle is a more common occurrence on the fire ground than a soft nozzle. Soft nozzles get immediately reports via urgent radio traffic, hot nozzles are uncomfortable lived with and are unfortunately gated down at the bale to reduce nozzle reaction.  These hot and soft nozzle conditions are hazardous and should minimized with frequent appropriate hose and nozzle wet drills. 

(Part II) Nozzle Reaction as it Relates to Nozzle Pressure

Along with adequate residential suppression flow, the nozzle reaction developed by the 7/8-inch smooth bore tip and the 15/16-inch smooth bore tip of 60 lbs and 69 lbs, respectively, are within the ability of an initial hose team of two firefighters to handle when utilizing 1 ¾ -inch hose.  This is mainly attributable to the 50 psi nozzle pressure,which produces a low nozzle reaction. Low nozzle reaction is a critical component to producing a more maneuverable attack hoseline package.  The other components related to deployability of an attack handline package are primarily equipment related such as hoseline size/weight, charged and uncharged, and nozzle-bail type and shape.  A large 2 ½-inch handline,although more difficult to maneuver due to increased charged weight, also acts to absorb more of the nozzle reaction based on its inherit increased mass.

For the following discussion please use Table #2 as a reference.  If the flow rate in a hoseline were to remain constant, while nozzle pressure was doubled, one would expect a significant rise in nozzle reaction.  This rise in nozzle reaction would be due to the increased force and velocity of the stream.  A flow of 170 gpm will be used as an example. A ¾-inch smooth bore tip pumped at 100 psi would generate a flow of around 167 gpm, but a nozzle reaction of 88 lbs would also be developed.  A similar 170 gpm flow in a 7/8-inch smooth bore tip would require a 55 psi nozzle pressure, but only produces a 66 lbs nozzle reaction.  Now look at the advantage of enlarging the nozzle diameter to 1 1/8-inch tip (normally deployed on 2 ½-inch hose);this would develop a flow of 252 gpm at 45 psi and produce a reasonable 89 lbs nozzle reaction.This represents a significant increase in flow with roughly the same nozzle reaction as the ¾-inch smooth bore tip pumped at 100 psi nozzle pressure.

At this point,one might ask about horizontal reach and penetration. Does a drastic nozzle pressure change, above 40 psi and yet below 100 psi, significantly affect the horizontal nozzle reach of the common handline smooth bore tip sizes ranging from ¾-inch through 1¼-inch? Not as much as one would think. The maximum horizontal range difference between these three tips cited in the preceding paragraph is about 15 feet. These distance figures were calculated using a proven horizontal reach formula, HR = 1/2 NP +26 (Purington 279).  However, the volume difference is about 85 gpm.  Note that when stepping up to the 1 1/8-inch smooth bore tip the horizontal range difference is about 10 feet, but also note the vast increase in flow for the same nozzle reaction.The reason that 50 psi is a good operating nozzle pressure for handline smooth bore tips(and fog nozzles)is that it gives the firefighter an effective reach of around 60 feet for 7/8-inch and 15/16-inch tips,and 70 feet for 1 1/8-inch and 1¼-inch tips, while maintaining acceptable nozzle reaction and flow rate. Although it attains the required 160 gpm for safe residential fire suppression, the ¾-inch smooth bore tip, pumped at 100 psi, has an unacceptably high nozzle reaction of 88 lbs for an initial 1¾-inch attack handline package supported by a nozzle team of one or two firefighters.

So, what is acceptable handline nozzle reaction? The nozzle reaction force must not exceed that force which can be overcome by a hose team assigned to the attack handline without excessive nozzle control issues. A suitable handline nozzle reaction is one that will allow development of effective flow and reach yet will not quickly exhaust the hose team due to excessive exertion.  This ideal handline nozzle reaction must be manageable, within reason, throughout the incident. “Some instructors use a rule of thumb which states that a firefighter can safely handle one-half of his or her body weight in nozzle reaction force” (Fornell 195).  At the time of publication for Fornell’s book, a fair estimate for average body weight without equipment was around 200 lbs, putting acceptable nozzle reaction at 100 lbs.  This rule of thumb produces what the author considers a high acceptable nozzle reaction number for a single firefighter handline, and was most likely developed in the era of heavily staffed 2 1/2-inch hose lines pre 1970. 

Andrew Fredericks, a hose and nozzle instructor of national repute, commonly put the safe maximum nozzle reaction for a single firefighter at around 69 lbs.The author found a tolerable nozzle reaction, through experience as a hose and nozzle instructor, to be right in line with about 70 pounds for a “single firefighter” line. Single firefighter is in quotes because a minimum of two firefighters should be assigned to a 1¾-inch attack handline.  This second firefighter is more of a door/kink firefighter on a 1¾-inch attack handline and acts only occasionally as true back-up to the nozzle position.  Many fire departments staff up the initially pulled handline line as additional companies arrive on scene. This is to ensure the greatest likelihood of the initial attack handline making it to the seat of the fire.Proper staffing and placement are paramount for the initial attack handline. This improves mobility to the point where it can be driven to the seat of the fire, rapidly achieving extinguishment.  This will lead to a safer fire environment where the bulk of the fire has been rapidly knocked all the way to the seat of the fire. The more rapid the extinguishment, the greater the levels of safety, efficiency, and effectiveness for all other operations that must occur on the fireground.  Most fire departments with four or more personnel on engines routinely deploy 1¾-inch attack handline packages with a true hose team of a nozzle firefighter, back-up firefighter, and a door/kink firefighter at the outset of operations.

The high reaction force associated with the 15/16-inch smooth bore tip at 50 psi nozzle pressure requires a greater need for good nozzle technique and constant vigilance in operation, as it is unforgiving to the pump operator.  Pump operator error of just 10 psi too high produces a nozzle reaction of 83 pounds and a flow of 202 gpm in the 15/16-inch smooth bore tip.  A hot nozzle situation with a 15/16-inch tip can rapidly create an unsafe condition that can easily lead to a loss of nozzle control and failure to advance the line to the seat of the fire.  The 7/8-inch smooth bore tip is more forgiving of a hot nozzle condition. At 60 psi nozzle pressure the 7/8-inch smooth bore tip creates 72 pounds nozzle reaction and a flow of 176 gpm.  Both nozzles are routinely used in fire suppression. However, the 15/16-inch smooth bore tip requires more vigilance, ideal pump operation, and, ultimately, reasonable staffing for an adequate flowing advance and maneuverability inside a structure.  To argue with the physical universe is to tilt at windmills. Knowledge of actual nozzle reaction force and its consequences will lead to better deployed and understood attack handline packages, and ultimately more success in combating fire conditions.

(Part III) 2 ½-inch Hose Deployability and Optimum Flow

Now, to delve into the new and unknown world of the 1 3/16-inch smooth bore tip. An argument based on the physics and facts surrounding deployability and effectiveness on the fire ground shall now be presented as to why this nozzle should be considered the highest flow handline nozzle (300 gpm).  Again, several factors are now leveraging the fire service into addressing the need to examine optimum flow rate for 2½-inch hose. Predominating amongst these are modern hydrocarbon-heavy fuel loads, rapid fire development, energy efficient building construction, reduced staffing, and longer fire development before initial extinguishment efforts. It is the intent of this treatise to ensure that the fire service does not overlook a potentially very useful tip size and flow rate for 2½-inch handline operations.

Before we can address why the new nozzle size is needed, we should look at why the big guns of handlines, the 2½-inch attack packages, are so under utilized.  There have been many theories advanced.(McGrail, “Keys to Success Big Line”). Two of those carrying the most credence shall now be addressed. Firstly, use of the 1¾-inch attack handline has become institutionalized. In effect, the fire service has become a victim of its own success. As the routine stretching of 1¾-inch attack lines successfully combats the vast majority of residential and other smaller scale fires, the line has come to be seen as a panacea for all fire conditions. This often results in a conditioned response on the part of engine companies to stretch 1¾-inch hose regardless of size-up indicators. Secondly, the fear of difficulty in deploying 2½-inch line often leads to the selection of 1¾-inch hose even though its flow rate is insufficient for the given fire ground scenario. This leads to multiple 1¾-inch attack lines being stretched where a lesser number of well staffed 2½-inch attack lines would more safely, efficiently and effectively combat the given fire conditions. Why so many officers fail to recognize when a larger handline is appropriate and fail to take proper action is not a focus of this presentation. The ADULTS Acronym, popularized by Andy Fredericks, and many others, covers the time and place to pull a larger flow attack handline package as follows:

A —Advanced Fire Upon Arrival

D —Defensive Operating Mode (Defensive Operations)

U—Unable to Determine the Extent (Size) or Location of the Fire

L —Large, Uncompartmented Areas

T—Tons of Water (One ton of water per minute with a 1-1/8” tip)

S—Standpipe Operations

However, that being said, the fear of failure as it relates to deployability, will be addressed as the key factor, in this article, affecting under-utilization of 2½-inch attack handlines. Many personnel have had negative experiences, with large handlines, related to deployability, controllability, and maneuverability.  These experiences led to judgments that the high flow attack handline is ineffective because it cannot be effortlessly advanced to the seat of the fire. Lack of familiarity and training lead to the inability to move the line forward in an efficient manner.  Essentially, many crews view the 2½-inch handline as a defensive line anchored to one spot. This is regardless of the fact that an ADULTS fire requires the greater flow rate based on heat release rate and other factors dictating the need for the increased extinguishing capacity of 2½-inch hose. An examination of the history and physics behind many negative experiences with 2½-inch handlines is a necessary step on the road toward achieving greater utilization of this very important weapon in the fire service arsenal.

What is acceptable nozzle reaction for a 2½-inch attack handline package, which today typically flows between 250 and 325 gpm?  There is not as much material on this subject matter, as compared to that which is available regarding nozzle reaction for 1¾-inch lines. However, it is well understood that to have the best chance of properly deploying a 2½-inch attack handline package a back-up firefighter is required immediately.  It is also necessary to have a door/kink firefighter to feed hose and facilitate forward movement of the hoseline.  This means that if an engine company is going to deploy a 2½-inch attack handline package flowing 250 to 325 gpm it must immediately have three firefighters assigned to the line. A 2½-inch attack handline package can be deployed in a static aggressive defensive action, using the reach and penetration of the high flow stream, with only one firefighter and then transition to a mobile attack as staffing is augmented.

Table #4 contains a very common nozzle used to develop large handline flows, the 1 1/8-inch smooth bore tip. It produces a flow of 266 gpm with a nozzle reaction of 99 lbs.  This nozzle is well known to produce a functional, easily deployable, high flow hoseline when staffed with a nozzle firefighter and back up firefighter with a door/kink man to help push the line forward.  The high flow rate and great extinguishing capacity characteristics coupled with low nozzle reaction force cause it to be a true force multiplier. These qualities lead Chief David McGrail, and many others, to make it a mission to have this line put into routine service.  Other notable hose and nozzle instructors that consider this a very functional line are Daryl Liggins, Jay Comella, Aaron Fields, Jason Blake and Curt Isakson to name just a few.  The 1 1/8-inch smooth bore tip is also the 2 ½-inch handline nozzle choice for the FDNY, the largest urban fire department in the United States. This should speak volumes as to the true effectiveness of the 1 1/18-inch smooth bore tip and 2 ½-inch hose attack package.

The author’s initial negative experiences with 2½-inch hose are typical for many in the fire service from 1980 to 2000. 100 psi combination nozzles became commonplace on the fire ground. A common target flow rate of the time was 125 gpm for small handlines (often 1½-inch). This flow at 100 psi nozzle pressure only produced a reaction force of around 65 pounds. This is well below the 75 pound nozzle reaction limit to be considered a controllable small attack handline. The story was quite different as 100 psi combination nozzles encroached into the realm of the 2½-inch handline and displaced the old brass play pipes and smooth bore nozzles that operated at 50 psi nozzle pressure.

Two very common 100 psi large handline combination nozzles of the time were the adjustable gallonage 200/225/250 gpm and the fixed gallonage 250 gpm nozzles.  The salesmanship and fog stream theory of the time conspired to create a huge influx into the fire service of these 100 psi large handline nozzles. The adjustable larger flow 100 psi combination nozzles in most departments were usually set at 250 gpm, because the logical stance was if one were to pull a 2½-inch handline one would want to flow at least 250 gpm.  Table #3 demonstrates the high nozzle reaction forces many fire service professionals dealt with as they learned to operate 2½-inch handlines with 100 psi combination nozzles. High nozzle reaction force associated with this nozzle inevitably led to monumentally bad experiences.  Many are left with negative impressions ingrained in their memories of entangled hose straps, slipping feet, twisted knees, wrenched backs and shoulders. All of which led to slow forward progress of the line, even with large commitments of staffing. In an effort to avoid the inordinate reaction force, the member on the nozzle would often gate down the shut-off and/or select a fog stream. These efforts to reduce physical strain have the unfortunate effects of reducing water flow and stream reach.

Those collective bad experiences both on the drill ground and at fire scenes, directly contributes to the bad habit of pulling multiple 1 ¾-inch handlines.  This habit really takes root and becomes common place as flows start reaching 180 gpm at 50 psi nozzle pressure in small handline attack packages.   Most companies make the easy rationalization of pulling two 1 ¾-inch handline when faced one 2 ½ -inch handline attached to a 250 gpm @100 psi nozzle system.  The bad habit is forged into acceptable behavior all the way to the command staff level based on the fear of failure founded in the truth of high nozzle reaction generated by 100 psi nozzle pressure in larger attack line packages which lead to nonfunctional large handlines.  

Whether or not a handline is controllable boils down to one thing,and one thing only, the level of nozzle reaction force.  The red highlighting again represents negative consequences.  The green highlights again represent positive consequences.The yellow highlights represent the limits of flow and nozzle reaction.  Table #3 represents the exorbitantly high price in nozzle reaction for a given water flow when operating a 100 psi nozzle. There is no variance of these characteristics depending on nozzle manufacturer. It is based on physics. The same would even hold true for a smooth bore nozzle. For example a 15/16-inch smooth bore tip at 100 psi nozzle pressure produces a flow of 261 gpm and a nozzle reaction of 138 pounds (Fornell 225). 100 psi nozzle pressure, when used to generate flows of 250 to 300 gpm, produces a harsh, unforgiving, and unacceptability high nozzle reaction.These qualities were not of great consequence with the low, 60 to 125 gpm, flow from small handline combination nozzles of the 1950’s, 60’s, and 70’s. Due to the low volume of water being moved, excessively high nozzle reaction forces were not generated. However, the high flow 100 psi nozzle pressure, 200 to 300 gpm, large handline nozzles of the 1970’s, 80’s, and 90’s generated very high levels of nozzle reaction. The drive toward the increased use of combination nozzles was based on the misperception that there was a need to introduce a stream pattern of fine water droplets into the fire compartment. This is a theory that has been thoroughly disproven. See Bridge and Vestel, A Quantitative Approach to Selecting Nozzle Flow Rate and Stream, for a detailed examination of stream selection.

2½-inch hose with an 11/8-inch smooth bore tip operating at 50 psi nozzle pressure generates a reaction force of 99 pounds. With training, this is considered to be a manageable line to deploy. It has good controllability while flowing and advancing. 1¼-inch is the other currently accepted smooth bore tip size for use with 2½-inch hose.  Even with a low nozzle pressure of 50 psi, the sheer massive volume of water flowing through the 1¼-inch tip causes a high level of reaction force. At 50 psi nozzle pressure, the 1¼-inch smooth bore tip produces a flow of 328 gpm and a nozzle reaction of 123 pounds.  The high reaction force causes severely limited controllability, deployability, manageability, and maneuverability. Most hose and nozzle instructors will confirm that, even with three very proficient, physically fit, firefighters (filling the nozzle, back-up, door/kink positions), it is a very difficult endeavor to aggressively advance a 2½-inch line with a 1¼-inch smooth bore tip.

Based on the author’s experience as a hose and nozzle instructor, as well as consultation with other noted instructors such as, Comella, Liggins, Fornell and Isakson, the 123 pound reaction force associated with the 1¼-inch smooth bore tip is not practicably manageable while flowing and advancing.  Vincent Dunn states that flows above 300 gpm are master streams mainly based on reaction force (Dunn 102).  “At high rates of delivery, a handheld nozzle would be too difficult to control, so mechanical, electrical, or hydraulic assists are required” (Dunn 102). It is the author’s belief that a maximum nozzle reaction of 115 pounds lends itself to a functional, mobile, effective 2½-inch attack handline. This nozzle reaction is below what a 1¼-inch smooth bore tip develops at 50 psi nozzle pressure. 

A large county fire department, with roughly 600,000 citizens under its protection, is in the process of moving to a more controllable 2½-inch attack handline with which to combat ADULTS fires.  They currently use a 300 gpm at 100 psi combination nozzle on their 2½-inch handlines. With a reaction force of roughly 150 pounds it is rarely used.  The members of the department have chosen, based on research and testing, to move to a 11/8 -inch smooth bore tip at 50 psi nozzle pressure in order to reduce reaction force. This makes fora much more deployable 2½-inch handline.  After initial training they were able to efficiently deploy the new 2½-inch attack handline package with a three firefighter company.  They have used this line successfully at several ADULTS fires. Initial staffing on the line is two firefighters and the hose team is augmented as additional companies arrive.  Members’ assessments of the line’s performance bear out that its prompt deployment is more effective than stretching multiple 1¾-inch lines.

A 2½-inch handline proves more effective, in many ways, than do multiple 1¾-inch lines. Foremost is flow. A good goal for a department’s handline compliment is that a minimum of a 100 gpm flow difference exists between its small and large attack handlines.  100 gpm is a significant increase, which will lead to distinctly accelerated extinguishment when the larger line is chosen over the smaller.  Unlike two or more 1¾-inch handlines, the impact of a 2½-inch line is highly concentrated, thus magnifying its effect, as the stream is worked about the fire compartment leading to a higher percentage of water impacting both the superheated overhead and the burning solid fuels.  Physics dictates that it produces a stream that is much harder hitting. This is due to the mass of such a high volume of water concentrated in a single stream. Hence, the heavier stream has more power to knock out windows, penetrate compromised drywall, push aside drop-ceiling panels, and effectively coat the interior of the fire compartment with water. The same qualities that allow the 2½-inch hose stream to more effectively overcome physical obstacles also allow it to more effectively penetrate superheated gasses and create a higher droplet fall out rate, thus absorbing more heat. There is also a reach advantage of around 10 feet causing the stream to reach further out into large spaces than can multiple 1¾-inch handlines.

(Part IV) Attack Handline Package Solutions and the 1 3/16-inch Tip (or 300 gpm @50 psi Fog)

Based on the logic laid out above and the contributions many fire service professionals whom have come before in the fields of fire stream development, hydraulics, and basic hose deployment Table #5 was developed.  This table represents the three key factors whose interrelation dictates the degree of effectiveness of attack handline fire streams. These factors are flow rate or gallonage, nozzle reaction force, and horizontal reach.  The table is broken down into two nozzle systems. Each system is based on a given department’s choice of complimentary sizes of the smooth bore tips for its small and large attack handlines. One system is based on the choice of 7/8-inch and 11/8-inch tips. The other is based on the selection of 15/16-inch and 1 3/16-inch tips.  This shall be referred to as the rule of eighths and sixteenths.  

This two choice nozzle system is based on simplicity, physics, and community fire load. As of now, 1¾-inch and 2½-inch are the two most commonly used attack hose line sizes in the United States. There are strong arguments for a minimum flow difference of 100 gpm between a fire department’s handline attack packages.  A key component of a handline attack package is that it must be deployable as a true interior attack handline. Two options are presented as possibilities to increase simplification and functionality of handline attack packages.

•Option one should function well based on most communities’ fire loads. The lines are deployable with company staffing as low as three firefighters. The 7/8-inch smooth bore tip on 1¾-inch hose generates a controllable nozzle reaction force across a range of 40 to 60 psi nozzle pressure. It also provides a stream of sufficient flow for most residential fires.  The 11/8-inch smooth bore tip generates controllable nozzle reaction across a range of 40 to 55 psi nozzle pressure. It provides a 100 gpm increase in flow over the 7/8-inch smooth bore tip.  The 11/8-inch smooth bore flow of 266 gpm makes for an effective line for those fires which fall within the parameters of ADULTS.

•Option two operates at the acceptable limits of flow and nozzle reaction. This system is well suited for communities with high fire loads, significant exposure issues, and high occupancy density.  Departments choosing this option need company staffing of four or more firefighters per unit.  The 15/16-inch (185 gpm) and 13/16-inch (296 gpm) smooth bore tips represent the limits of controllable reaction force across a range of 40 to 50 psi nozzle pressure.  There is a minimum of 100 gpm difference in flow between the two lines. At 50 psi nozzle pressure, the 13/16-inch smooth bore tip generates a nozzle reaction force of about 111 pounds. This is below the 115 pounds nozzle reaction force that represents the maximum that is practicably sustainable for personnel.

The venerable 1¼-inch tip has held pride of place, as the largest smooth bore tip to develop a handline stream, for over 100 years.  However, it is basically not very functional or deployable in common practice. The 328 gpm flow rate comes at the exorbitantly high price of 123 pounds nozzle reaction force. This is well above that reaction force which is practicable for sustained control by personnel on an attack handline. 

Looking through older hydraulic texts one cannot help but notice the lack of a 15/16-inch smooth bore tip.  Lore has it that the Fire Department of New York developed it. FDNY engine companies felt that on 1¾-inch attack line they could handle more than the 60 pounds nozzle reaction force associated with the 161 gpm stream developed by a 7/8-inch tip at 50 psi nozzle pressure.  Yet many desired a reaction force less than the 79 pounds generated by the 210 gpm stream of the 1-inch smooth bore tip (known by various names such as a Bronx blaster and Harlem blaster).  Through necessity and ingenuity, the 15/16-inch smooth bore tip came into being. At 50psi nozzle pressure it flows 185gpm at 69 pounds reaction force.  Word has it that some companies still use their “blasters”, 1-inch smooth bore tips. However, the 15/16-inch smoothbore tip was rapidly well received based on both deployability and extinguishing capability. It was adopted as the 1¾-inch handline nozzle of choice, not only in New York City, but also, in many fire departments throughout the country.

Many departments could benefit from the use of the 13/16-inch smooth bore tip.  Some examples are:

•Los Angeles City Fire Department has a static bed of 2½-inch hose with a 1¼-inch smooth bore tip. It is not routinely deployed due to difficulty in controlling high nozzle reaction produced by the 1¼-inch tip causing over-reliance on small handlines.

•Chicago also uses the 1¼-inch tip with all of its above-stated high nozzle reaction disadvantages.

•FDNY with a less than 100 gpm difference in flow between their 1¾-inch hose with 15/16-inch tip and their 2½-inch hose with 11/8-inch tip would likely see benefits by moving up to a 13/16-inch smooth bore tip.

•Redwood City Fire Department is the only department in the San Francisco Bay Area that routinely deploys a 1¼-inch smooth bore tip and pumps it at a 40 psi nozzle pressure to reduce nozzle reaction.(A common practice)They,too,could benefit from the 13/16-inch smooth bore tip. 

Some, who are well-versed in standpipe operations, may question how a 13/16-inch smooth bore tip could be successfully deployed from a 65 psi standpipe outlet.  At 40 psi nozzle pressure, the 13/16-inch tip will basically replicate the 266 gpm flow of a 11/8-inch smooth bore tip at 50 psi nozzle pressure.  The main differences are a few feet shorter reach and a reduction of 10 lbs of nozzle reaction.  It may end up being easier to deploy off a 65 psi standpipe outlet based on less nozzle reaction. In addition, many standpipe systems deliver more than the minimum required 65 psi outlet pressure. Hence, routinely, greater heat absorbing 300 gpm streams can be achieved.  This issue, as well as others surrounding standpipe operations, needs to be addressed through testing and expert opinions. Hopefully David McGrail, and others possessing high degrees of experience and knowledge regarding standpipe operations, will find merit in addressing these issues. 

(Part V) Moving Forward the 1 3/16-inch Tip (or 300 gpm @50 psi Fog)

In conclusion, the same logic behind the successful acceptance and implementation of the 15/16-inch smooth bore tip may also end up to be the impetus behind the successful acceptance and implementation of the 13/16-inch smooth bore tip.  For small attack handlines, the flow and reaction force characteristics of the 15/16-inch tip make it the happy median between the 7/8-inch and 1-inch smooth bore tips. For large attack handlines, the same concepts dictate that the 13/16-inch tip is the happy median between the 11/8-inch and 1¼-inch smooth bore tips. The evidence is too great to continue to ignore the potential of the 13/16-inch smooth bore tip any longer.Time and experience will bear outthe need for the 13/16-inch smooth bore tip. Some prototype 13/16-inch smooth bore tips are now being produced for research, testing, and training purposes.  Flow testing will be performed.Some of the most experienced hose and nozzle instructors will evaluate the 13/16-inch tip. Perhaps in the near future it will no longer be considered, “the missing tip”.

In regards to what will become of all those 1¼-inch smooth bore tips currently being used in the fire service, the following is offered. The 1¼-inch smooth bore tip, at 50 psi nozzle pressure, has a reaction force too great for handline operations.However, it may still be useful. The 1¼-inch smooth bore tip, at 80 psi nozzle pressure, flows 415 gpm with a reach of 86 feet. It would be best deployed on a rapid attack monitor. This flow could be supported by a single 2½-inch line and, as David McGrail might put it, becoming the first step from rifle to artillery.

In solidarity,

Dennis LeGear


Works Cited

Akron Brass Company.  Akron Brass 2008 Product Catalog.  Wooster: Akron Brass Company 2008

Bridge, Eric A. and Vestal Jason N.  “A Quantitative Approach to Selecting Nozzle Flow Rate and Stream,            Part1”.  New Jersey: Fire Engineering 1 October 2010

Bridge, Eric A. and Vestal Jason N.  “A Quantitative Approach to Selecting Nozzle Flow Rate and Stream,        Part 2”.  New Jersey: Fire Engineering 1 January 2011

Dunn, Vincent. Command and Control of Fires and Emergencies. New Jersey: Penn Well / Fire               Engineering. 1999

Clark, William E.   Firefighting Priniciples and Practices.   2nd Edition.  New Jersey: Penn Well / Fire            Engineering. 1990

Fornell, David P.  Fire Stream Management Handbook.  New Jersey: Fire Engineering. 1991

McGrail, Daivd.  “Keys to Success with the "Big Line": Proper Weapons Selections”  California: Fire Nuggets            Website. 


Noted Contributors

Jay Comella (Capt. Oakland Fire, ret.)                       -for editing, adjustment to prose, conceptual consultation.  


Geoffrey Hunter (Capt. Oakland Fire)                       -for grammatical editing.


Curt Isakson (BC Escambia Fire)                               -for motivation and consultation.


Veronica Wunderlich (ES, Dept. Water Res., CA)    -for grammatical editing.

Hose Dreams

Author: Dennis J LeGear, Capt. Ret. Oakland Fire, CA

Uncommon thoughts about commonly used suppression equipment: information to aid in the selection of proper handline hose diameter (fire hose's dirty little secret).

Introduction:  History Repeating

The fire service is once again focusing on a topic that garnered a lot of attention in the 80’s and 90’s. Many are now revisiting the concept of attaining higher than standard flows through 1.75-inch hand-lines.  1.75-inch hand-line flows of 250gpm are being considered. This flow in small diameter hand-line is, in many ways, damaging to all fire ground operations because it limits the functional envelope of the stretch to around 200 feet due to high friction loss.  Creating two distinctly different flows from one size hose-line also adds to fire ground confusion by complicating pump operations and line selection. 

Company level issues begin with a tunnel vision that sees a hose stretch of 200 feet as sufficient for the commercial fire ground.  A limited stretch length capacity will cause the Officer and the Engineer to consider poor engine placement, blocking critical truck placement real estate in front of and at the corners of buildings.  There is great potential for time intensive and dangerous hose pack deployment if the stretch should fall short.  It complicates pumping operations by producing two friction loss numbers in one size line. Other complications likely to arise are: two nozzle pressures (NP) in a single fixed orifice nozzle system, a set of stacked tips, or the complicated automatic hand-line nozzle.  It increases likelihood of line failure do to greater internal forces created by high pump discharge pressure.  It complicates multiple hand-line operations off one pump due to high pump pressure differences between large and small hand-line sizes attaining large flows.   

Command and Chief level issues will include the following negative impacts on the fire ground. There will be an inability to determine flow by simply looking at the deployed hand-lines.  Large hand-lines and small hand-lines should always be spec’d in contrasting jacket colors, thus aiding command in determining fire flows.  There will be a reduction in total flow capacities on the fire ground because, as pump pressure increases pump capacity decreases.  There will be difficulty in placing second alarm companies, especially trucks, due to initial alarm engine companies striving to get within their 200 foot envelopes of function. The increased complexity of operations, training, and equipment purchasing will have been submitted to for a slightest possible benefit. 

The author has spent over a decade studying this, and the true necessity of keeping it simple cannot be overstated.  The goal of most fire departments should be a single small attack line flow of 160-185gpm (staffing of 2-3 firefighters) and a single large attack line flow of 250-300gpm (staffing of 3 plus firefighters). This should be generated in two distinctly different hose sizes while maintaining a reaction force and charged hose-line weight that produces a mobile attack hand-line capable of aggressive interior operations.  If you have not yet read Nozzle Dreams, the author urges you to do so before going further. 
What size is your handline fire hose, really?

Only a change to the NFPA 1961: Standard on Fire Hose, where language such as “hand-line fire hose (2.5-inch and smaller) will be within a 1/16th of an inch of what is printed on the jacket at 150psi operating pressure and never exceed a 1/16th of an inch of what is printed on the jacket below 300psi”, will solve this problem.  This is a manufacturing problem. It is also a failure of leadership in the fire service.  Right now fire departments are receiving hand-line fire-hose that is, de facto, not what was ordered or specified.  We will continue to revisit this destructive situation regarding flows and hose-line sizes, which has clear answers based in physics, repeatedly until the root cause is addressed.  The problem is “internal diameter hose creep” leading to the creation of “mystery hose”.    

Advancements in Hose

The greatest reduction in friction loss in modern fire hose has been created both accidentally and later intentionally by increasing the internal diameter of charged fire hose.  It started when the thicker double jackets of cotton were replaced by mold resistant thinner double jackets made of nylon and polyester. At this time the rubber liner remained, however the bowl size of the coupling remained the same leading to a slight increase in the internal diameter of charged fire hose. 

Recently, with the invention of lightweight hose, the problem was amplified.  Lightweight hose rapidly became the worst offender because the new thinner liners and jackets created a larger internal diameter as coupling bowl size either remained the same or were intentionally made larger in some lightweight hose designs. This gave lightweight hose a larger diameter when charged. This increase in size lowers the friction loss at a given flow and increases the volume of water in the hose.  This also means it is heavier when deployed, because it is carrying more water inside of it when charged.  Do not let the hose brochure or salesmen mislead you. All of the fire hose manufacturers have access to the same, or similar, technology. They are working on a basically level playing field with regard to material and process.  Fire hose, at best, has about the same friction loss coefficient as smooth plastic pipe such as PVC. 

Lightweight hose is also more prone to failure under fire conditions from mechanical and thermal insult. This is due to the lightweight construction and the corresponding reduction in mass. That is why most lightweight hose comes with a 5 year warranty instead of a 10 year warranty.  A useful analogy from building construction is lightweight versus legacy construction under fire conditions.  NFPA 1961 should also now require a fire exposure test that includes heat and direct flame contact components.   As molten plastic becomes more common on the fire ground, hose-line durability must be ensured.  Please note Image #1. The Oakland Fire department (OFD) has experienced both close burn through and complete burn through of charged hose-lines resulting in near misses.  Currently OFD uses a rubber lined, nylon double jacketed handline hose of the same spec that is in the picture.  The damaged hose in the picture extinguished the fire without loosing waterway integrity. It is the author’s opinion that lightweight hose would have failed under the interior attack conditions that caused this significant hose damage.

Image #1         Fire damaged traditionally constructed rubber lined, nylon double jacketed hose

This article will build a case demonstrating the existence of this “internal diameter hose creep” in two ways. First, mathematically, using a Hazen-Williams equation calculator and later by a method of direct measurment.  Remember that the engineering standards and coefficients that will be used in this article have a proven track record of decades.  The friction loss numbers generated by the equation literally have hundreds of thousands of hours and thousands of miles of pipe backing up their validity. The physical universe controls movement of water through both pipe and fire hose. The results are known quantities and are outside the control of hose manufacturers.  It is a constant here on Earth.        

Four Mathematical Proofs that Manufacturers are Gaming Us.

Proof #1   (1.75-inch?) 

As for 1.75-inch hose flowing 250gpm at 50psi friction loss per 100 feet, it would have to be as smooth as PVC pipe and be 1.9 inches in diameter.  This was the entire point of a 2.5-inch Alternative? article in the Oct. 2013 issue of Fire Engineering magazine. It is not 1.75-inch hose.  The author of the article even admits to it being larger then 1.75-inch double jacketed (DJ) fire hose and then continues calling it 1.75-inch DJ fire hose.  Note below, in Table #1, the diameter required for the flow of 250gpm with a friction loss of 50psi per 100 feet. It is clearly 1.9 inches in diameter. 

Table #1         Diameter of Hose Required to Flow 250gpm per 100 feet at 50psi is Almost 2-inches (Hazens-Williams Formula)

Many departments, including FDNY and Miami-Dade, have been misled by this lack of transparency in hose manufacturing.  The new lightweight 2-inch hose with 2.5-inch coupling is probably closer to 2 1/4-inchs under operating pressure, based on the manufacturer’s given friction loss numbers.  It has been reported to the author by an FDNY member that some of this hose has actually failed under storage conditions by sticking together. Lightweight hose with a thermoplastic polyurethane liner also has a well-documented high rate of delamination failure of the waterway, in which the liner separates from the inner jacket.  This problem can lead to total clogging of a nozzle and is an automatic failure in all hose testing procedures.  

In the Oakland Fire Dept, over 21,000 feet of lightweight 4-inch supply hose, with this type of liner, was recalled for delamination. Since fire departments are no longer in the practice of keeping the equivalent of three hose loads for every pumper (one for the rack, one for the tower, and one for the rig) the OFD had a big problem.  Good practice now is to have the equivalent of two hose loads, with a 5 year separation in age and an anticipated 10 year service life.  Many fire departments can not afford this, and this amount of failed hose can not be ordered quickly, it must be manufactured.  The OFD quickly tested 4 miles of 20-year old auxiliary hose wagon DJ 5-inch hose of traditional rubber lined construction.  Less then 10 lengths failed a 250psi 5-minute pressure test after years of negligent care and storage. This is a true testament to how good traditional rubber lined hose construction and jacket/liner bonding is.  It was common in the past to have well cared for fire hose of double jacketed cotton, rubber liner, design pass service tests at the 30-year mark.          

Should the FDNY, and the fire service, be experimenting with new intermediate light-weight hose sizes that are nearly disposable or demanding a return to true 2.5-inch hose, the actual solution!?  A true 2.5-inch hose is truly 2.5-inches and is made from proven construction methods to ensure reliability, dependability, and consistent size and performance throughout its 10-plus-year life span.  We will be addressing the significant disservice that internal diameter hose creep has done to 2.5-inch hose shortly in this article.   

Proof #2   (2-inch with 2.5 Couplings)

Again in Fire Engineering magazine, an article entitled High-Rise Buildings (April 2013) features this new 2-inch hose with 2.5-inch couplings.  A claimed friction loss of 25psi per 100 feet at a flow of 250gpm was achieved.  The author is positive that Bill Gustin, a luminary in the fire service, correctly performed both flow and friction loss testing. However, the hose is likely 2.2-inchs in actual diameter if we are to believe the waterway is as smooth as PVC pipe.  This of course means it is not actually 2-inch hose.  See Table #2

Table #2         Diameter of Hose Required to Flow 250gpm per 100 feet at 25psi is at least 2.2-inches (Hazens-Williams Formula)

Proof #3(2-inch?) 

Internal diameter creep in fire hose manufacturing is a problem that is industry-wide.  However, Key fire hose provides clear friction loss numbers for their hose-line.  Key ECO-10 fire hose claims 7.5psi friction loss in their 2-inch hose at 185gpm in 50 foot lengths. It is assuredly the FL you will get if you test it.  It is also, assuredly, not 2-inch hose and is probably 2.2 inches in diameter when charged.  Note in table #3 the diameter required for a flow 185gpm, with a friction loss of 7.3psi per 50 feet, is clearly 2.2 inches.

Table #3         Diameter of hose required to flow 185gpm per 50 feet at 7.5psi is at least 2.2-inches (Hazens-Williams Formula)

Proof #4(2.5-inch?) 

The problem of internal diameter size creep has even more repercussions in 2.5-inch DJ fire hose. Even a small increase in size significantly reduces residual pressure at common hand-line flows of 250 to 300gpm, increasing kinking. It also significantly increases charged hose weight.  Knowledge has grown in this area with more testing of OFD’s current 2.5-inch hose spec completed earlier in the year (2013).  The author has become increasingly concerned with departments jumping to lightweight 2-inch hose with 2.5-inch couplings without acknowledging the significant internal diameter size creep in 2.5-inch hose.  This information was shared with many departments, including the FDNY during testing of 2-inch fire hose. 

The OFD completed a 5 year project around 2007 to increase the use of larger flows, specifically a 265gpm 2.5-inch hand-line flow at warranted fire conditions.  The author was charged with development of a “Pump Chart” and some of the flow testing.  At the time the author served as the Water Supply Officer (WSO) as well as a line Captain and sat as an advisor on the Engine, Truck, and Hose Committees.  The Hose Committee chair, Daryl Liggins, with assistance from Jay Comella and others, put forth a traditional construction nylon DJ 2.5-inch hand-line hose with a rubber liner as the final selection after extensive testing of many other options and manufacturers.

This selected hose provided a friction loss in departmental flow testing of roughly 9 psi per 100 feet of hose at 265gpm.  We had no reason to doubt the manufacturer’s claimed internal hose diameter of 2.5-inchs.  It was also a big step in the right direction for the OFD, because at the time members routinely deployed that flow from 3-inch fire hose. 3-inch hose, due a heavy charged water weight, was virtually impossible to aggressively advance without the use of hose straps and standing nearly erect, making it a purely exterior defensive hose-line and stream.  The OFD was moving towards the common 2.5-inch hand-line size to be utilized in standpipe operations and interior operations at commercial fires.

The OFD picked a hose that was the best members could find at the time, but still substantially larger than “true 2.5-inch fire hose”.  To achieve a friction loss of 9psi per 100 feet of hose at 265gpm, the OFD 2.5-inch hose must be at least 2.75-inch in actual diameter. Please note the results in table #4, and again realize that this is the case only if the fire hose is as smooth as PVC. It may actually be a bit larger than 2.75-inch internal diameter.  However, OFD 3-inch hose is prone to be 3.25-inch in actual diameter, so this represented a vast improvement in reduction of charged hand-line weight.  3-inch hose should not be used as a handline for this very reason, as the Author stated in Fire Engineering’s Handbook for Firefighter I and II

able #4          Diameter of Hose Required to Flow 265gpm per 100 feet at 9.5psi is at least 2.75-inches (Hazens-Williams Formula)

A Visual Proof Manufacturer’s are Gaming Us.

The visual example is OFD spec 2.5-inch Double Jacketed Nylon with Rubber liner.  You will need a pair of internal and external calipers.  (Calipers provided by late Engineer Bob Comella, OFD retired).  Bob Comella has provided a wealth of knowledge to the author over the years in firematics. These tools will provide you the ability to make the necessary measurements.  With these measurements one will be able to find the “true diameter” of your department’s hose.  The author strongly urges you to ascertain all of these measurements, as seeing is believing.  However, you only need steps 4 and 6 to attain the best results. Handling fire hose in its component parts is also an educational process in itself, providing a direct account and tactile experience as it relates to durability and construction.  You will find cutting lightweight hose much easier due to the significantly less robust construction.      

Step 1 (Figure A) Find the bowl diameter; it is very common for it to be 3-inches in 2.5-inch hose.

Figure A 3-inch Coupling Bowl for 2.5-inch DJ Nylon Rubber lined hose

Step 2 (Figure B) Cut hose off coupling as close as possible.  Measure it.  The 2.625-inch measurement is inaccurate; the material made it a difficult to measure with a ruler. Still note, it is visually larger then 2.5-inches before it is put under pressure. 

Figure B - 2.5-inch hose cut off at the coupling

Step 3 (Figure C) Then reach into the coupling with a pair of internal measurement calipers and measure the diameter at the expanded expansion ring.  As you can see it is 2.812 inches.  This is the second visual cue that hose size creep exists, probably due to thinner jackets and liners. 

Figure# C - 2.8125-inches Expansion Ring Measurement - 2.5-inch Nylon DJ Rubber Lined hose

Step 4 (Figure D) Determine the thickness of total jackets and liner material.  Lightly clamped in wood, it measured 0.3125 inches. 

Figure D - 0.3125-inch DJ Nylon & Rubber Liner Material Thickness in 2.5-inch Hose

Step 5 (Figure E) Use external measurement calipers to gain a diameter measurement at both operating pressure and 100psi static.  No significant difference was found. 

Figure E  - External caliper measurement of diameter of charged 2.5inch hose

Step 6 (Figure F) Record the external diameter measurement of the hose.  It was 3.062 inches.  Notice it is larger then 3-inches.  Some hose construction designs allow for more diameter expansion through stretching.  Try to spec as close to a static/fixed external diameter hose construction under reasonable 100 to 200 psi pump discharge pressures as possible.  This type of hose construction can be expected to minimize problems with liner separation, increase longevity and provide predictable friction loss characteristics.

Figure F - External caliper measurement of diameter of 2.5-inch hose

After you have attained the above information, you can gain the most accurate internal diameter measurement of the charged 2.5-inch hose.  It will be provided by subtracting the Step 4 measurement of 0.3125 inches (total DJ Nylon Rubber Lined Material Thickness) from the Step 6 measurement of 3.062 inches (external diameter of the charged hose).  This math yields a result of a true diameter of 2.75 inches in OFD 2.5-inch fire hose. 

The author was being conservative with the caliper measurements and made sure it was snug against the hose when measuring external charged diameters. Oakland spec DJ attack hose is at least 2.75-inchs, probably a bit more if you take into account slight hose expansion when charged.  Lightweight hose would cut down on jacket and liner material thickness, so the result with the standard 3-inch coupling bowl for 2.5-inch hand-line would be an even larger internal diameter.  This creates a tragic “Catch-22” for lightweight hand-line hose construction. It is lighter to carry when uncharged, but heavier when charged to deploy. It is also inherently more prone to failure.  Talk about a bad deal. 

The internal diameter creep in modern 2.5-inch hand-line leads to a significant impact on deployment in the form of unnecessarily low friction loss for common handline flows, even off standpipes, and increased charged water weight.  The weight issue is clearly denoted by Figure G. It gives internal hose diameter in 1/8ths of an inch from 2 1/2-inch to 2 7/8-inch true internal diameter hand-line.  Note the roughly 70 pound weight difference between the smaller and larger of the listed line sizes.  Chiefs, spec your hose wisely for your rank and file!   

Figure G - Water weight difference in 2.5-inch fire hose with different internal diameters

What size diameter “true hose” line do we need?

The Nozzle Dreams article reached this point and developed a two choice nozzle system that is based on simplicity, physics, and community fire loading.  As of now, 1¾-inch and 2½-inch (roughly 1.85 and 2.75 inches respectively) are the two most commonly used attack hose-line sizes in the United States. There are strong arguments for a minimum flow difference of 100gpm between a fire department’s handline attack packages.  

Table#5 represents the three key factors whose interrelation dictates the degree of effectiveness of attack hand-line fire streams. These factors are flow rate or gallonage, nozzle reaction force (RF), and horizontal reach.  The color scheme in Table#5 dictates that red highlighting represents negative consequences.  The green highlights represent positive consequences.  The yellow highlighting represents the limits of flow and nozzle reaction for hand-line operations. The table is broken down into two nozzle systems. Each system is based on a given department’s choice of complimentary sizes of the smooth bore tips for its small and large attack hand-lines (or fixed 50psi Fog Nozzles). One system is based on the choice of 7/8-inch and 11/8-inch tips. The other is based on the selection of 15/16-inch and 13/16-inch tips.  This shall be referred to as the rule of eighths and sixteenths.    

Table #5 - The rule of 1/8ths and 1/16ths is a simple two nozzle system for fire service hand-lines

A key component of a hand-line attack package is that it must be deployable as a true interior attack hand-line.  Charged hose-line weight is a large factor in deployability, note in table 5 the far left side is hose size.   True internal diameter, 1.75, 2, or 2.5-inch, DJ hand-line probably does not currently exist. Remember, when examining Table 6 below, it has been well established that 69 pounds is the largest acceptable reaction force for small attack-line operations. This allows for a deployable fire stream of 185gpm at 50psi nozzle pressure. Also, 111 pounds is the upper limit of reaction force for a large hand-line with a flow of 295gpm at 50psi.  Please take note that hand-line operating pressure should ideally not exceed 200psi and more normally operate in the 100 to 150psi range.  The author also acknowledges that many factors on the fire ground can realistically lead to a range of nozzle pressures. Hence, the 40 to 60psi nozzle pressure spread provided in Table#5.  We must not get bogged down in a system that requires perfect execution, this will lead to failure on the battle ground. Where pump operators, officers, and hose-line members are operating in a task saturated and time compressed environment, efficient simplicity is the key to effective attack package deployment.  As much as possible should be addressed before contact with the enemy.         

Notice that the 1-inch tip flowing 210gpm generates a reaction force that is high for a small hand-line but low for a large handline. Essentially, it leaves flow under-developed in a properly staffed large hand-line, but it has a reaction force too great for a lightly staffed hand-line of 2 firefighters. The 1-inch tip flow of 210gpm has largely been abandoned by the fire service. It has had a recent resurgence, but it is probably an off-course idea. The color scheme in Table# 6 dictates that red highlighting represents negative consequences.  The green highlights represent positive consequences.  The yellow highlighting represents less than acceptable flow (below 250gpm is used for commercial fires and standpipe operations) and heavy charged hose-line weight for a lightly staffed line.  Note in table 6, a perfectly good 240gpm stream can be produced with the same reaction force of 79 pounds using a 1 1/8-inch tip. The 1 1/8-inch tip used in this manner, under pressurized at 40psi, leaves a significant reserve capability of developing a true large flow fire stream of 250gpm or greater.  This is what the author recommended to the FDNY for their “actual 2.2-inch” 50 foot standpipe pack hose.  It is the authors understanding that this hose is now used as the lead length for tenement standpipe operations utilizing a 1-inch tip.  Advice was also given to take a closer look at the diameter of their 2.5-inch hose spec, which is likely where answers to the deployability issues truly lie and greater department-wide benefits could have been realized, by operating with a “true 2.5-inch diameter handline.”    

This would have also aided departments nationally. For often, as the FDNY goes, so go many of the nation’s urban fire departments and equipment manufacturers.  There are many issues revolving around this move in the FDNY and as an outsider one can not know all of the facts even when invited to comment and given some background.  Some department members have made it clear that, in their opinion, in the past tenement fires were dealt with using an attack package consisting of a lead length of FDNY 1.75-inch hose (1.88inch) with a 15/16th tip (185gpm) filled out with 2.5-inch hose. Many considered this flow more than adequate for fire control and extinguishment at certain tenement standpipe fires. Those outside of the FDNY must take into consideration that there are no pressure regulating valves (PRV) on standpipe systems in New York City. As per city code, there are only pressure reducing devices (PRD).  SOPs dictate that Members remove PRDs for standpipe operations. This means that achieving higher standpipe outlet pressure is only limited by the test pressure of the system.  Contributing factors of flow path control and line management issues where brought up extensively when talking about failure and success in tight stair and hallway configurations found in tenement type buildings in the City of New York.  It is very commendable that the FDNY is attempting to address these issues; their efforts in these matters are probably not yet exhausted.           

Table#6 -“True Diameter Hose” Handline Selection Tab  

RF = 1.57 x (D)sq x NP          GPM = 29.7 (D)sq √NP         (Fornell)

What has eluded Miami-Dade and FDNY, and so many others, is that they are fielding 2.5-inch hose that is probably at least 2.75-inches. This adds 70 more pounds of water weight per 100 feet than necessary.  Additionally, much of the rest of the fire service deploying 2.5-inch “mystery hose” is using traditional hydraulic formulas or pump charts and over pressurizing nozzles. This leads to excessively high flows and nozzle reaction forces.  Many who flow test 2.5-inch “mystery hose”, discover a low friction loss per 100 feet, which leads to low pump discharge pressures at 265gpm flows.  This leads to low residual pressure in 2.5-inch “mystery hose”, which increases kinking and line management issues. 

You may note a 1 1/8-inch tip with a 265GPM flow at 50psi NP generating a substantial friction loss of 45 psi per 100feet hose, deployed on 2-inch true handline hose in Table #6.  Fire departments that routinely operate from standpipes or deploy lengthy stretches of large flow handlines would be better serviced by a return to a true diameter 2.5-inch hand line hose.  The recent focus on having hose manufacturers create a “2-inch mystery hose” actual 2.25-inch diameter hose, may be a misguided attempt to overcome the problems created by“hose diameter creep” in current 2.5-inch DJ handline fire hose, which is 2.75-inches in actual diameter and larger. Efforts should be made nationally to address this problem first, before the need for 2.25-inch hose is evaluated.

The ideal attack hand-line hose diameters for a fire department will depend on their selection within the range of small hand-line flows (160-185gpm) and within the range of large hand-line flows (250-295gpm).  It is critical to keep one size of hose for large attack hand-line flows.  The hose must be of a size that is practical to deploy from a large static bed to facilitate multiple lengthy stretches without having to deal with a different size lead length of hose. This is the ideal!  The hose must be of a size that will work well for standpipe operations and deliver an adequate flow when deployed from a standpipe outlet with a PRV set to 65psi.  That hose does not need an internal diameter of 2.75-inches or the new 2.25-inch lightweight hose diameter.  Physics dictate the answer again. The hose-line needs to be 2.5-inchs in diameter. No more, no less. This is based on the commercial hand-line fire stream goal of 250-300gpm.  It is with good reason that it was that size to begin with.

To add clarity to the line selection process, this article adds two items under “L” in the A.D.U.L.T.S. list of conditions necessitating the use of 2.5-inch hose.

A — Advanced Fire Upon Arrival

 D — Defensive Operating Mode (Defensive Operations)

 U— Unable to Determine the Extent (Size) or Location of the Fire

 L — Large, Uncompartmented Areas, Lengthy Stretch, Low Pressure Possibility

 T— Tons of Water(One ton of water per minute with a 1-1/8” tip)

 S   — Standpipe Operations

An A.D.U.L.T.S diameter hand-line hose must be capable of a large flow that will work on standpipes and for very lengthy stretches while maintaining deployability.  This should be a call to return to the “true 2.5-inch hose”.  All other special situations can easily be addressed by filling out true 2.5-inch DJ hose with 1.75-inch or 2-inch DJ fire hose.  Remember to keep it simple.  Members pump these handlines under less than ideal conditions.  In the OFD, a pump operator needs only to remember four numbers 50, 30, 10, 5.  All nozzle pressures are 50 psi. 30psi per 100 feet is the friction loss in 1.75-inch hand-line hose (160gpm). 10psi is the friction loss in 2.5-inch hand-line hose (265gpm) per hundred feet. Lastly, 5psi is the friction loss in 2.5-inch hose per 100 feet when used to fill out 1.75-inch hose line. 

Table 7 is the first three lines of the OFD pump chart with a picture of the rear static bed. It is color coded to reflect the proper hose line.  We must set our people up for success. Unnecessary complication on the battle ground of a structure fire, may rapidly lead to a series of cascading failures ultimately leading to inability to extinguish the fire at the seat in a rapid fashion.  Line selection for the officer between small, 160gpm, and large, 265gpm, flow should be clear.  Lengthy stretches should be easily attainable in both small and large flow hand-lines allowing the crew to focus on getting the nozzle to the seat of the fire.  No hose-packs or wyes should be necessary to deploy hose from the pumper.  Ideally there should only be two shut offs in a deployed line, one at the pump panel and other the other at nozzle.   

Table# 7 - Partial OFD Pump Chart and Picture of Rear static loads

The fire service members are the end users of the product.  One is hard pressed to think of any other industry that allows this degree of manipulation in an engineered product.  Water main systems we rely on are all mathematically developed based on known internal pipe diameters and friction loss coefficients.  Can you imagine ordering a 30 foot ladder and being delivered a 33 foot ladder? People would immediately complain.  Many respected instructors in this field, including Curt Isakson, Ray McCormack, John Ceriello, Jay Comella, Daryl Liggins, Jerry Herbst, Jason Blake, Jeff Shupe, Jerry Knapp, David McGrail, Dave Fornell, myself and others teach that you must flow test your hose to determine friction loss. This wrongly suggests that hose is magical and somehow deviates from known hydraulic formulas.  It’s the hose, not the formula that is lying. “Mystery Hose” has been created by many influences.  The path to this dysfunction was paved with bricks of good intention. Only the truth and transparency will put us once again on the right path! We must demand it! Only a change to the NFPA 1961: Standard on Fire Hose, where language such as “hand-line fire hose (2.5-inch and smaller) will be within a 1/16th of an inch of what is printed on the jacket at 150psi operating pressure and never exceed a 1/16th of an inch of what is printed on the jacket below 300psi”, will solve this problem.

Which Chief or Department will stand up and be the first to return out of spec hose?  Which manufacturer will end this shell game and ensure honesty with a “true hose jacket diameter marking”? There has been a real cost to this “hose diameter creep”.  Operating with a hand-line larger than needed for the developed flow creates or exacerbates many line management issues including increased kinking, additional water weight in the line, increased nozzle reaction force, and greater difficulty in flowing water whilst advancing the line. “Hose diameter creep” has national impact, as countless slowed fire attacks lead to increased property damage and endangered lives. 

The fire service would be well served by three true hose diameters of 1.75, 2 and 2.5-inch.  The vast majority of the fire service need only to field true hose diameters of 1.75-inch and 2.5-inch. This hand-line fire hose should be of traditional construction with a double-jacket of nylon or polyester and a rubber liner. Hose of this construction should carry a minimum 10-year warranty.  This provides the lightest possible charged hose weight, while ensuring the robustness, durability, and reliability inherent in traditional hose construction. Maneuverability is well served and quick attack bread and butter residential fires can be combated with appropriate flows of 160 to 185gpm through true diameter 1.75-inch hose.  A true diameter 2.5-inch hose has the versatility to function at all A.D.U.L.T.S fires, and reclaims the mobility it has lost over the years due to “internal diameter hose creep” having burdened members with up to 70 pounds of unnecessary water weight per 100 feet of hose.       

It is the author’s intent to fix this problem on a national scale.  The coefficient of friction loss for smooth PVC plastic pipe was used in the above examples and an online Hazens-Williams hydraulic formula calculator.  PVC plastic pipe coefficient was intentionally selected in order to give fire hose manufactures the best possible scenario. The results clearly show that hand-line fire hose is commonly cheated up in size above the marked jacket diameter. This is one of the largest problems facing the fire service. As we increase our fire flow to deal with higher heat release rate in modern fire loading, most of us have addressed reaction force by lowering nozzle pressure. The fire service must strive to reduce hardships members collectively suffer while advancing hose-line on the fire ground.  In the end, members deploying large flow handlines are reaction force limited to roughly 110 pounds produced by 295gpm at 50psi.  Physics dictates that the fire service should not be fielding a hand-line with a diameter larger then 2.5-inchs.  

In solidarity,

Dennis LeGear



Works Cited


Bill, Nemick“A 2 ½-Inch Alternative?”. New Jersey: Fire Engineering 1 October 2013

Corbett, Glenn. Editor Fire Engineering’s Handbook For Firefighting I and II. Oklahoma: PennWellCorporation. 2009

Fornell, David P.  Fire Stream Management Handbook.  New Jersey: Fire Engineering. 1991

Gustin, Bill“High Rise Buidlings”.  New Jersey: Fire Engineering 1 April 2013

“Know Your Flows”.  Key Hose. Website.

 Online Hazens-Williams Calculator.  Engineering Tool Box Website.


Noted Contributors

Jay Comella (Capt. Oakland Fire, ret.)                       -for editing, adjustment to prose, conceptual consultation.  

Curt Isakson (BC Escambia Fire)                               -for motivation and consultation.

Veronica Wunderlich (ES, Dept. Water Res., CA)    -for grammatical editing.

Other Instructors Mentioned in Article                      -for advancing and pushing my curiosity