Water Flow Rate Calculator
Pipe Flow (Velocity)
Calculate flow rate from pipe diameter and velocity
From Pressure (Hose/Nozzle)
Estimate flow rate from pressure and orifice size
Bucket Test
Measure flow rate with a bucket and timer
Formula
Q = A × V | Q = Cd × A × √(2gh) | GPM = ft³/sec × 448.831 | Head (ft) = PSI × 2.307
Frequently Asked Questions
How do I measure my water flow rate?
Use the bucket test: turn on the faucet or hose fully, time how long it takes to fill a 5-gallon bucket, then divide 5 by the seconds and multiply by 60 to get GPM. For example, 30 seconds = 10 GPM.
What is normal residential water pressure?
Normal residential water pressure is 40-80 PSI, with 50-60 PSI being ideal. Pressure below 30 PSI is too low for most fixtures. Pressure above 80 PSI should be regulated to prevent pipe damage.
How many GPM do I need for my house?
A typical home needs 8-12 GPM for simultaneous use of multiple fixtures. Each fixture uses: Shower 2-2.5 GPM, Faucet 1.5-2 GPM, Toilet 3 GPM (during flush), Dishwasher 1.5 GPM, Washing machine 3-4 GPM.
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