There room two ways to calculation friction loss: the theoretical an approach or the fireground method — here's the fireground method


One of the pump operator’s major goals is to provide the fire attack crew through the necessary water flow to gain their project done. There are plenty of points that the pump operator must gain done in the early on stages the a fire, and also none are more important 보다 this.

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One the the pump operator’s an essential tasks is determining what pump discharge press to set for every supply or hand line. To identify this, the pump operator must very first know the full gallons per minute flow, the is, the desired result on the working end of the hose.

The type of nozzle being supplied — smooth-bore, automatic nozzle or adjustable gallonage — will recognize the gpm. As soon as the pump operator to know what the wanted gpm is, climate they must recognize what dimension hoses space being used, the lengths the the hoses and also any appliances the are part of the hose layout, such as a gated wye.


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Armed with that information, the pump operator deserve to then calculate the friction loss, the staying ingredient for obtaining the best mixture to their firefighting colleagues.

Friction is the pressure resisting the relative motion of heavy surfaces, liquid layers and material facets sliding versus each other. Friction loss is the press loss because of the friction.

In the fire organization application, the friction is water sliding versus the internal surfaces of the pump, any kind of connected appliances — gated wyes, manifolds or a water theif — standpipes and fire hose.

Pump operators need to commit these five friction loss values to memory.

every fire hose has friction loss.There is no collection friction ns for any kind of one dimension of hose.Friction ns is established by the gpm flowing, the dimension of the hose and also the size of the hose. All three factors must it is in considered.Most the the fog nozzles have flow rates varying from 95 to 200 gpm. Don’t acquire stuck ~ above one circulation rate; the fire will certainly dictate which circulation rate to use.It’s no psi that puts the fire out; it’s offering the correct gpm the the occurrence commander needs.

Getting comfortable with friction loss

Truly understanding friction lose is critical for all pump operators, and also it’s commonly presented to new pump operators as something akin to knowledge quantum physics. In reality, expertise friction loss and also its ar in appropriately supplying hose lines and fire streams is not that challenging of a task.

The basic an obstacle for the pump operator is to construct the proper pump discharge pressure important to conquer the friction ns in a fireground collection up to ensure that the firefighter on the nozzle will have actually the suitable amount the water to suppress the fire.

There are two ways to calculation friction loss: the theoretical technique or the fireground method. The previous uses math equations, when the last uses rules of ignorance that nothing require much in the method of mathematics calculations. 

Theoretical calculations are generally finest used for pre-fire planning, arising specifications for pumping apparatus and also calculating difficulties ahead the time, together as developing pump charts. Theoretical calculations are generally not an efficient way of calculating friction loss on fire scenes.

Many times, instructors to teach pump operations carry out the theoretical method, in addition to its equations, at the start of the maintain process. It’s your mistaken id that knowing how the clock is built is necessary for the watch owner come know before they learn exactly how to call time utilizing the watch.

I was really fortunate at the start of my firefighting career to join a department wherein that was no the case.

My pump operator instructors focused early on on developing my an abilities in utilizing such devices as the hand technique for calculating friction loss. They likewise emphasized memorizing the friction loss because that the pre-connected hand lines and typical hose layouts the I would certainly encounter together a pump operator.

A hose construction that would be employed at an apartment or condominium complex, because that example, was 200 feet the 3-inch supply hose, linked to a gated-wye, offering two 13/4-inch fire assault lines the 200 feet each v a 100-psi adjustable fog nozzle on every line set for 150 gpm.

The hand method

This is one extremely beneficial tool because that both learning and also teaching what the friction ns is for miscellaneous sizes of hose and various gpm flows. Below is one example of a hand technique for calculating friction loss in various sizes the hose.


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utilizing the hand method, because that each 100-foot length of 1¾-inch water tap flowing 200 gpm, the friction loss is 48 psi: 2 x 4 x 6 = 48 psi. Because that a 3-inch supply heat flowing 300 gpm, the friction loss every 100-foot section would be 9 psi: 3 squared amounts to 9 psi.

Memorizing this much simpler than the sounds. Simply memorize the friction loss for the gallonage settings top top the nozzles offered in her department. Most 100-psi adjustable fog nozzles because that use through 1¾-inch water tap have 4 settings: 95 gpm, 125 gpm, 150 gpm and 200 gpm.

All you have to remember is the friction loss because that each, 14, 24, 35 and also 62, respectively. Those room the amounts of friction loss per 100 feet of hose based on the gallonages above. 

Thus, the friction loss every 100 feet the 1¾-inch hose once flowing 95 gpm is 14 psi; because that a 200-foot line, her friction ns is 28. It functions the same method for the other gallonage settings. 

Change the flow setting on the nozzle come 150 gpm top top the exact same 100-foot line and also the friction loss is 35, if you rise the hose length to 200 feet, the friction loss becomes 62 psi.

Don’t forget, this is just the friction loss in the hose; it is no the pressure that you have to generate from the pump at the engine. To number the compelled discharge pressure, include up all friction ns — in the hose and also any appliances — plus the forced nozzle pressure.

Thus, for that apartment facility layout I pointed out earlier, the calculation would look prefer this:


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Know your friction loss points

perform your homework around the different hose loads, appliances and nozzles offered in your department and what every contributes come friction loss, that is, what space the friction loss points. A finest practice employed by countless skilled pump operators is creating a cheat paper containing what those friction loss points watch like.


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Source: University that Alaska, Fairbanks. The Physics of Fireground Hydraulics. April 2011.

My fire organization colleague through the Henrico ar (Va.) department of Fire, Taylor Goodman, offers one more perspective ~ above friction loss. There is friction loss in ~ the inner plumbing the the fire device itself.

“Even pumpers ordered indigenous the very same manufacturer utilizing the same spec deserve to have differences in their internal plumbing,” stated Goodman, “resulting in different required PDPs indigenous one engine come another.”

Per Goodman, the only means to truly determine an accurate PDP for a certain pumper is come test each discharge v a flow meter. Time consuming, because that sure, but an ext accurate.

Goodman additionally said that few of the nation’s leaders in fire streams and their applications, such together Dennis LeGear, have figured out that over there is no typical national traditional in determining the inner diameter in between manufacturers for various diameter strike lines.

“This creates several issues when friend teach a nationally accepted an approach for determining friction loss, then put a circulation meter on it and also find that you"re in reality 20 pounds off,” claimed Goodman.

According come Goodman, there"s a grassroots effort to upgrade the standards, as well as working with the manufacturers, to bring some consistency to those inner diameters and also anticipated friction loss in ~ the internal plumbing of fire apparatus.

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Battalion chef Robert Avsec (ret.) offered with the Chesterfield (Virginia) Fire & EMS Department for 26 years. He was an instructor for fire, EMSand hazardous products courses at the local, state and federal levels, i m sorry included more than 10 years through the nationwide Fire Academy. Chief Avsec earned his bachelor’s level from the college of Cincinnati and also his master’s level in executive fire business leadership from grand Canyon University. He is a 2001 graduate of the national Fire Academy's EFO Program. Past his composing for gaianation.net and FireChief.com, Avsec writer the blog talking "Shop" 4 Fire & EMS.Connect through Avsec top top LinkedIn orvia email.