Pool Pipe Flow & Velocity Calculator
Check how quickly water moves through a pool pipe at a given flow. Enter GPM and actual inside diameter to calculate feet per second, then compare common PVC Schedule 40 sizes using the same flow and your selected design-velocity limit.
Convert flow and actual pipe inside diameter into water velocity. Compare pipe sizes at the same GPM.
How to use this calculator
The calculator distinguishes nominal pipe size from the inside diameter used in the math. It also reports flow capacity at the velocity limit you enter, making it easier to discuss a branch line, equipment connection or proposed plumbing change with an installer.
- Enter the flow that passes through the individual pipe or branch.
- Select a Schedule 40 example or enter the pipe’s measured or specified inside diameter.
- Choose the appropriate design limit and review velocity and the size comparison.
Worked example
At 60 GPM, a pipe with a 2.067-inch inside diameter has a calculated velocity of about 5.74 feet per second. That falls below an entered comparison limit of 6 feet per second. The chosen limit is illustrative; it does not establish compliance or the permitted suction or return velocity for a particular installation.
Example inputs illustrate the calculation. Enter your own measurements, product directions and rates to plan your pool.
Turn your result into a plan
Pair velocity checks with the TDH calculator to consider system resistance. A larger pipe changes the velocity at a given flow, but actual pump flow also depends on the pump curve and the complete system. Confirm valve and fitting connection dimensions before ordering.
Explore related equipment
Review these product pages as part of your equipment planning. Confirm model, installation and system compatibility before ordering.
Frequently asked questions
Can I use nominal size as the inside diameter?
No. Nominal size is a size designation. The calculation needs actual inside diameter, which can vary with material and wall thickness. The preset list supplies Schedule 40 example dimensions.
Should I enter total pump flow for every branch?
Only if all that water passes through the pipe being checked. Parallel branches carry portions of system flow, so use the individual branch’s flow whenever possible.
Is 6 feet per second always an allowed limit?
No. It is the tool’s editable comparison example. The permitted value depends on the branch, equipment and applicable requirements. Have the installer verify the correct limit.
Does this calculate friction loss or suction safety?
No. It calculates cross-section, velocity and capacity at a selected limit. Use the TDH tool for head estimates, and have suction protection and code compliance assessed separately.
Continue your pool planning
Need help choosing pool equipment?
Send Pool Supply Depot your pool size, calculator results and existing equipment details. We can help review product options and the information to confirm with your installer. Based in Henderson, Nevada, we serve pool owners and pool professionals nationwide.
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