Water Pressure Calculator (Static vs Dynamic)

Static pressure is what you read on a gauge when everything is closed - the pipe is full and resting. Dynamic pressure is the scene during a shower: water moving through pipes, losing head to friction and elevation on the way to the fixture.

Water Pressure Calculator walks the pressure budget from the main to any fixture: subtract the elevation loss and the friction loss, and you see the dynamic pressure the fixture actually receives.

• Static vs dynamic: Compare pressure at rest and under flow.
• Elevation loss: 0.433 PSI per foot of rise.
• Friction estimate: Hazen-Williams loss for the run.
• Velocity check: Flags noisy or erosive pipe speeds.
• Verdict: Adequate, marginal or low for typical fixtures.
• Export: Copy or download the report.

1. Enter the main static pressure you read at the meter or tank.
2. Enter the fixture elevation above the main in feet.
3. Set the design flow and pipe size for the worst fixture or fixture group.
4. Add pipe length and material for the friction estimate.
5. Compare static vs dynamic and check the verdict.

Example 1 - Two-storey home. 55 PSI main, fixture 14 ft up a 3/4 in copper line, 40 ft run at 6 GPM: static at the fixture is about 48.9 PSI, dynamic under flow roughly 47 PSI - comfortable.

Example 2 - Long 1/2 in run. 60 PSI main, 1/2 in PEX, 15 GPM to a garden area: friction alone can eat 20+ PSI over 100 ft, dropping dynamic pressure below code minimums.

• See the real pressure: Not just the gauge at the main.
• Find the problem floor: Elevation and friction exposed.
• Preliminary check: Before choosing a booster or repipe.
• Free and private: No uploads, no logging.