Friction Loss Formula

Learn how to solve friction loss (fire hose pressure loss) with the friction loss formula. See simple examples of solving friction loss formula. Use a scientific calculator, a standar calculator or even solve the equation by hand. Use the online Friction Loss Calculator to verify your answer(s).

FL = C * (Q / 100) ^2 * L / 100

FL = Friction loss in PSI
C = Friction loss Coefficient (Table 1)
Q = Flow rate in GPM
L = Hose length


Example:

What is the friction loss for a 200 foot of 1.75 inch hose flowing 150 GPM of water?

Coefficient (C) for 1.75" hose is 15.5 (See Table 1)
GPM (Q) = 150 GPM
Length (L) = 200 feet

FL =  C  *  (Q  / 100) ^2 *   L   / 100
69.75 = 15.5 * (150 / 100) ^2 * 200 / 100


Answer: There's 69.75 PSI friction loss for a 200 foot of 1.75 inch hose with 150 GPM.

Answer verified in the friction loss calculator

Table 1
Friction Loss Coefficient
Hose Diameter Coefficient
0.75 inch 1100
1 inch 150
1 ¼ inch 80
1 ½ inch 24
1 ¾ inch 15.5
2 inch 8
2 ½ inch 2
3 inch 0.677
3 ½ inch 0.34
4 inch 0.2
4 ½ inch 0.1
5 inch 0.08
6 inch 0.05


Now, solve some some friction loss equations on your own:

What is the friction loss of 200 feet of 1.75" hose with 200 gpm? Answer 200' of 1.75" @ 200 GPM

What is the friction loss of 150 feet of 2" hose with 500 gpm? Answer 150' of 2" @ 500 GPM

What is the frictin loss of 100' of 1" hose with 100 gpm?Answer 100' of 1" @ 100 GPM

What is the frictin loss of 300' of 3" hose with 600 gpm?Answer 300' of 3" @ 600 GPM

What is the frictin loss of 400' of 3" hose with 800 gpm?Answer 400' of 4" @ 800 GPM

Verify your own friction loss problems with Friction Loss Calculator


Friction Loss Explained
Friction loss occurs when water passes through a hose. Hose length, diameter, and GPM (volume) all affect friction loss. As water passes through a hose, friction between the water and the inside surface of the hose causes turbulence, which slows the water. The results in a PSI drop (pressure loss) at the other end of the hose. The higher the gpm passing through a hose, the more turbulance and friction loss will result.

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