Each plumbing fixture uses water at a typical rate, measured in gallons per minute (GPM) or gallons per flush. These figures help size supply lines and water heaters.
| Fixture | Typical flow |
|---|---|
| Bathroom faucet | 1.5 GPM |
| Kitchen faucet | 1.5 – 2.2 GPM |
| Shower head | 1.8 – 2.5 GPM |
| Toilet | 1.28 – 1.6 gal/flush |
| Dishwasher | 1 – 2 GPM |
| Washing machine | 3 – 5 GPM |
| Hose bib | 5 – 9 GPM |
WaterSense limits. Efficient faucets are capped at 1.5 GPM and shower heads at 2.0 GPM. Add up the fixtures likely to run at once to size your supply and heater.
FAQ
Why does fixture flow rate matter for pipe sizing? Undersizing a pipe or branch line relative to total fixture flow demand causes pressure drop and poor performance when multiple fixtures run at once, which is why plumbing codes size branch lines and mains based on total fixture unit demand, not just the number of fixtures.
See the PEX Pipe Dimensions and Water Pressure Guide.