Water Pressure & Elevation Head Calculator
See how much of your street pressure actually reaches a fixture. Lifting water uphill costs pressure at 1 psi for every 2.31 ft of height, and friction takes more — this tool subtracts both so you can spot a low-pressure problem before you plumb it.
Calculator
Starting at 60 psi, lifting water 20 ft costs about 8.7 psi, leaving roughly 51.3 psi at the fixture (before friction beyond what you entered). Most fixtures want 40–60 psi; a PRV protects the house if the street pressure is high.
Homeowners usually blame “low water pressure” on the utility, but the pressure you actually feel at a fixture is what’s left after two deductions: the height the water had to climb and the friction it fought along the way. Height is fixed by your floor plan; friction grows with pipe length, fittings, flow and undersized pipe. This calculator isolates the elevation term so you can tell how much of a shortfall is simply physics.
Formula
Static pressure at a fixture is the supply pressure minus the pressure spent lifting the water and minus pipe friction:
psi_at_fixture = supply_psi − (height_ft ÷ 2.31) − friction_psi
The constant 2.31 is the number of feet of water column that equals 1 psi. Turn it around and every 10 ft of height ≈ 4.3 psi of lost pressure — the reason a top-floor shower feels weaker than the basement laundry.
Worked example
Street pressure is 60 psi; the second-floor shower head sits 20 ft above the meter; ignore friction for a first pass.
- Elevation cost: 20 ÷ 2.31 = about 8.7 psi.
- Pressure at the head: 60 − 8.7 = about 51.3 psi.
Comfortably in the 40–60 psi range most fixtures want. If the street delivered 45 psi instead, that shower would see only about 36 psi — noticeably weak, and a candidate for a pressure problem hunt.
Reading your pressure
Fixtures are happiest between roughly 40 and 60 psi. Below about 40 psi showers feel weak and appliances fill slowly; above 80 psi you risk noisy pipes, running toilets, stressed washer hoses and premature valve wear — and most plumbing codes require a pressure-reducing valve (PRV) when the street pressure exceeds 80 psi.
If your measured pressure is fine at the hose bib but weak upstairs, elevation and friction are the usual culprits, not the utility. If it is weak everywhere, look at a clogged PRV, a partly closed main shutoff or an old galvanized service line. Measure static pressure with the house idle, then measure again with a couple of fixtures open to see how much friction is eating — a big gap points to undersized or scaled pipe. Feed a friction estimate from the friction-loss tool back into this one for a more complete picture.
Reference table
| Height above source | Pressure lost | Left at fixture |
|---|---|---|
| 0 ft | 0.0 psi | 60.0 psi |
| 10 ft | 4.3 psi | 55.7 psi |
| 20 ft | 8.7 psi | 51.3 psi |
| 30 ft | 13.0 psi | 47.0 psi |
| 40 ft | 17.3 psi | 42.7 psi |
Elevation only, from your entered supply pressure (friction not included). 1 psi ≈ 2.31 ft of water column.