# Hazen-Williams Equation Head Loss due to Friction

Written by Jerry Ratzlaff on . Posted in Fluid Dynamics

This head loss due to friction formula is used in Hazen-Williams equations.

### Hazen-Williams Equation Head Loss due to Friction Formula

$$\large{ h_f = \frac { 4.73\; l \; \left( \frac {Q}{C} \right) ^{1.852} }{d^{4.87} } }$$     (US units)

$$\large{ h_f = 4.73 \left( \frac {Q}{C} \right) ^{1.852} \frac{l}{d^{4.87}} }$$     (US units)

$$\large{ h_f = 10.7 \left( \frac {Q}{C} \right) ^{1.852} \frac{l}{d^{4.87}} }$$     (SI units)

Where:

$$\large{ h_f }$$ = head loss due to friction

$$\large{ Q }$$ = flow rate

$$\large{ C }$$ = Hazen-Williams Coefficient

$$\large{ d }$$ = pipe inside diameter (ID)

$$\large{ l }$$ = length of pipe