Poly Pipe Size Calculator (Friction Loss)

Rough friction loss for a farm water line.

Uses the Hazen-Williams formula with a C value for smooth plastic pipe. It's a rough planning estimate; fittings, bends and valves add more loss. Everything is worked out in your browser. Nothing is saved or sent anywhere.

1. The line

Inside, not outside, diameter. Check the supplier's chart.
Negative if downhill.

2. Pressure

3. Results

How it was worked out

    What this does and doesn't tell you

    • Check the pipe's pressure rating (PN) is above the highest pressure in the line.
    • Ask an irrigation supplier to check long or complex lines.
    • This is a planning estimate only. Check the maker's instructions and your local council's rules before you build or buy.
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