# Closed Conduit Hydraulics - Hazen Williams Equation

Hazen-Williams can be used to determine the flow characteristics in closed conduits (pipe systems).

### For Velocity

S = slope, in decimal form. This is equivalent to

R = hydraulic radius,

C = Roughness Coefficient, get this from a tableĀ (available in both theĀ AIOĀ andĀ CERM)

### For Head Loss

To derive theseĀ has been substituted for S.

The Hazen-Williams equation is similar to the Darcy-Weisbach equation, but it is **only used for turbulent flow.**

### When to use Hazen-Williams

- You are only given C
- You prefer it and are sure the flow is turbulent (Reynolds number (Re) > 4000)
- You are directly told to (from the examples it looks like several problem prompts do this)

### When to NOT use Hazen-Williams

- The flow is NOT turbulent (Re < 2100)
- You are given . If you are given a friction factor use Darcy-Weisbach

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