Should fittings be included in the run length?

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

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.

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.

Question

Should fittings be included in the run length?

Accepted Answer

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.

Should fittings be included in the run length?

Answers