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IPC Ch.6
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How it works
Enter your values
Type in your inputs — the app fills code tables and constants for you, so there's nothing to look up.
Get a code-checked result
Instant answer with a clear PASS / FAIL and the exact IPC Ch.6 reference behind every number.
Save & export
Keep a history of calculations and export a clean PDF report to share or attach to a permit (Pro).
What this calculator does
Water pipe sizing makes sure every fixture gets enough flow and pressure without oversizing the system. This app follows the IPC Chapter 6 approach: total the water supply fixture units (WSFU), convert them to a probable demand in gallons per minute, then size the pipe to deliver that flow within the available pressure and a safe velocity.
How it works
- Add up the WSFU for every fixture on the run.
- Convert WSFU to peak demand in GPM using Hunter's curve.
- Size the pipe so velocity stays at or below about 8 ft/s (less on hot-water lines) and the friction loss fits the available pressure.
Worked example
A small house totaling about 20 WSFU has a probable demand near 15 GPM. To carry that under 8 ft/s, a 3/4-inch service or main is typical, stepping down to 1/2-inch at individual fixtures.
Related calculators
Total the units with the fixture unit calculator and check pressure drop with the head loss calculator.
Water pipe sizing FAQ
What code does it follow?
The IPC Chapter 6 water-distribution method: water supply fixture units converted to demand in GPM, then pipe sized for that flow within the available pressure and velocity limits.
Why limit velocity?
High velocity causes noise and erosion-corrosion, especially on hot-water copper. Keeping velocity at or below roughly 8 ft/s (and lower on hot lines) protects the piping.
Does it account for available pressure?
Yes. It compares friction loss, elevation, and fixture demand against the supply pressure so the most remote fixture still gets its required flow.
Does it work offline?
Yes, it runs 100% offline with no account. Free with rewarded ads; a one-time $2.99 Pro unlock adds PDF export and saved history.
Get Water Pipe Sizing on your phone
Free with rewarded ads · $2.99 lifetime Pro · iOS & Android. Works 100% offline on the job site.