Plumbers
Pipe Size Calculator
Determine the right pipe diameter for your water supply line based on flow rate and velocity.
Minimum pipe ID required: 0.825″ at 6 ft/s. Nearest standard size: 1" (ID: 1.049″). Applies to copper, PVC, CPVC, and PEX. Local codes and pressure calculations may require a larger size.
Common Questions
What size pipe do I need for a bathroom?
A full bathroom with a toilet, sink, and shower typically needs a 3/4 inch supply line. Individual fixtures can be served by 1/2 inch branch lines.
How do I size a water supply pipe?
Add up the flow rate in GPM of all fixtures that could run at the same time. Size the pipe so water velocity stays between 4 and 8 feet per second. This calculator finds the minimum pipe diameter for your flow rate.
What is the recommended water velocity in supply pipes?
Keep velocity between 4 and 8 feet per second. Faster than 8 fps causes noise, water hammer, and pipe erosion. Slower than 4 fps reduces pressure and can allow mineral buildup.
How many GPM does a typical home need?
A typical home uses 6 to 12 GPM peak demand. A shower runs about 2.5 GPM, a kitchen faucet about 2.2 GPM, and a toilet flush about 1.6 GPM. Add up the fixtures you expect to run at the same time.
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