# Hazen-Williams Coefficient

Hazen-Williams coefficient, abbreviated as C, also called Hazen-Williams friction coefficient, a dimensionless number, is used in the Hazen-Williams Equation. The lower the coefficient, the smoother the pipe is. The higher the coefficient, the less fluid flow is restricted. By using pipe materials with improved flow characteristics, energy costs for pumping can be reduced or smaller pipes can be used.

Note that the Hazen-Williams Coefficient is '''not''' the same as the Darcy-Weibach-Colebrook friction factor, f. These are not in any way related to each other.

## Hazen-Williams coefficient formulas

\(\large{ C = \frac {v}{ 1.318 \; r_h^{0.63} \; m^{0.54} } }\) | (mean flow velocity) |

\(\large{ C = \frac {Q}{ 0.285 \; d^{2.63} \; m^{0.54} } }\) | (flow flow rate) |

### Where:

Units |
English |
Metric |

\(\large{ C }\) = Hazen-Williams Coefficient, see below for values | \(\large{ dimensionless }\) | |

\(\large{ Q }\) = flow rate | \(\large{\frac{ft^3}{sec}}\) | \(\large{\frac{m^3}{s}}\) |

\(\large{ m }\) = hydraulic grade line slope | \(\large{ dimensionless }\) | |

\(\large{ r_h }\) = hydraulic radius | \(\large{ ft }\) | \(\large{ m }\) |

\(\large{ v }\) = mean flow velocity | \(\large{\frac{ft}{sec}}\) | \(\large{\frac{m}{s}}\) |

\(\large{ d }\) = pipe inside diameter | \(\large{ in }\) | \(\large{ mm }\) |

## Hazen-Williams Coefficient Table

Material | Hazen Williams Coefficient |
---|---|

Aluminum | 130 - 150 |

Asbestos Cement | 120 - 150 |

Asphalt-lined iron or steel | 140 |

Brass | 130 |

Cast Iron, cement lined | 140 |

Cast Iron, coated | 110 - 140 |

Cast Iron, new unlined | 130 |

Cast Iron, old unlined | 40 - 120 |

Cast Iron, uncoated | 100 - 140 |

Cast Iron, 10 years old | 107 - 113 |

Cast Iron, 20 years old | 89 - 100 |

Cast Iron, 30 years old | 75 - 90 |

Cast Iron, 40 years old | 64 - 83 |

Cement lining | 140 |

Concrete | 100 - 140 |

Concrete, old | 100 - 110 |

Copper | 130 - 140 |

Corrugated Metal Pipe | 60 |

Corrugated Steel | 60 |

Deteriorated old pipes | 60 - 80 |

Ductile Iron | 120 - 145 |

Fiberglass | 150 |

Galvanized Iron | 100 - 120 |

Glass | 130 |

Lead | 130 |

Polyethylene | 140 |

PVC, PE, GRP | 120 - 150 |

Steel, new unlined | 120 |

Steel, 15 years | 200 |

Steel, riveted joints | 95 - 110 |

Steel, welded joints | 100 - 140 |

Steel, welded joints, lined | 110 - 140 |

Steel, welded or steamless | 100 - 120 |

Tin | 130 |

Wood Stave | 110 |

Tags: Coefficient Equations Pipe Sizing Equations Hazen-Williams Equations