What is the Hazen-Williams equation for sprinkler friction loss?

Q: Which C-factor should I use for fire sprinkler pipe?

Use the project or standard-specified value. Typical first-pass values are around 120 for steel, 140 for ductile iron, and 150 for CPVC/plastic. Always match the value required by your design basis and AHJ expectations.

Q: Should fittings be included in the run length?

Yes. Convert fittings and valves to equivalent length and add them to straight-pipe length before calculating friction loss; otherwise the drop will be understated.

Question

What is the Hazen-Williams equation for sprinkler friction loss?

Accepted Answer

In US customary form, pressure loss is ΔP = 4.52 × Q^1.852 × L / (C^1.852 × d^4.87), where Q is flow in GPM, L is length in feet, C is roughness coefficient, and d is inside diameter in inches. The calculator applies this form directly.

What is the Hazen-Williams equation for sprinkler friction loss?

Answers