# Friction Loss Formula

Learn how to solve friction loss (fire hose pressure loss) with the friction loss formula. Below, you'll see an example of solving the friction loss formula. We have also provided several friction loss problems for you to solve & provided a links to the answer for each problem. If you create your own problems, you can check your answers with the Friction Loss Calculator

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 fire 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, use the friction loss formula to solve some problems 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 friction loss of 100' of 1" hose with 100 gpm?Answer 100' of 1" @ 100 GPM

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

What is the friction 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 turbulence and friction loss will result.