Friction Loss

Friction Loss

Estimate how much pressure is used up moving water through hose.

What It Tells You

How much pump pressure is lost to friction in a hose layout.

Formula

FL = C × (Q ÷ 100)² × (L ÷ 100)

What the Variables Mean

FL
friction loss PSI
C
the hose coefficient unitless
Q
flow through the hose GPM
L
hose length feet

Plain-Language Explanation

Friction loss is pressure used up pushing water through hose. More hose creates more loss, and increasing flow makes friction loss rise very quickly.

Worked Example

Flow 185 GPM through 200 feet of 1¾-inch hose using C = 15.5.

  1. Q ÷ 100 = 1.85
  2. L ÷ 100 = 2
  3. FL = 15.5 × 1.85² × 2
FL ≈ 106 PSI

Fireground Takeaway

Doubling flow through the same hose raises friction loss about four times because flow is squared.

Practice This Formula

Open Reverse Flow and start a Practice Quiz filtered to this topic.

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