← Back to All Tools
🚰

PVC Pipe Water Flow, Velocity & Friction Loss Calculator

Calculate water velocity (ft/s), Hazen-Williams friction pressure head loss (PSI / 100 ft), and dynamic GPM flow capacity in Schedule 40 and 80 PVC pipes.

Calculation Results

Water Flow Velocity: 4.14 ft/sec Optimal Velocity (Between 2 and 5 ft/s)
Friction Loss Rate: 1.46 PSI / 100 ft
Total Pipe Run Pressure Drop: 2.19 PSI (5.06 ft total head loss)
Actual Internal Diameter (ID): 2.067 inches

About This Calculator

Calculate water velocity (ft/s), Hazen-Williams friction pressure head loss (PSI / 100 ft), and dynamic GPM flow capacity in Schedule 40 and 80 PVC pipes.

Frequently Asked Questions

What is the maximum recommended water velocity in PVC pipes?

Uniform Plumbing Code (UPC) and civil engineering design standards recommend a maximum water velocity of 5.0 feet per second (ft/s) for cold water supply piping and 8.0 ft/s for short irrigation service runs to prevent water hammer and pipe erosion.

Why does Schedule 80 PVC have higher friction loss than Schedule 40?

Both Schedule 40 and 80 have the same outside diameter (OD); however, Schedule 80 has a much thicker pipe wall to withstand higher internal pressures, resulting in a smaller inside diameter (ID) and higher flow resistance.

What is the Hazen-Williams roughness coefficient C for PVC?

PVC pipe has an extremely smooth hydraulic bore with a Hazen-Williams C-factor of 150 (compared to C = 100 for unlined ductile iron or C = 130 for copper), resulting in minimal friction head loss.

How do you convert head loss in feet to pressure drop in PSI?

Multiply hydraulic head loss in feet of water by 0.4335 (or divide by 2.31). For example, 10 feet of friction head loss equals 4.335 PSI of pressure drop.