Water Pressure Converter

1 psi = 6.9 kPa ≈ 2.31 feet of water head, and 1 bar = 14.5 psi = 100 kPa ≈ 33.9 feet of head. Feet of head is the most physical of the four: it is literally how high the pressure can push a column of water, which is why tanks and pumps are often specified in it.

The height of a water column the pressure supports — every 2.31 ft of elevation adds 1 psi (about 0.69 m per 0.1 bar). It works both ways: a tank 20 ft above a faucet delivers about 8.7 psi (0.6 bar), and a pump must add 1 psi of pressure for every 2.31 ft it lifts.

US municipal supply typically arrives at 40–80 psi (about 3–5.5 bar / 300–550 kPa), and many codes cap it at 80 psi. Fixtures are happiest between about 30 and 60 psi (2–4 bar); below 15 psi (1 bar) showers feel weak and some mixers and tankless heaters won’t operate properly, while sustained pressure above 80 psi (5.5 bar) strains hoses, valves and water heaters — a pressure-reducing valve is required above 80 psi.

US residential water heaters are typically rated to 150 psi maximum working pressure, protected by a temperature-and-pressure (T&P) relief valve — elsewhere cylinders (geysers) are rated 400 or 600 kPa with a matching pressure-control valve. Either way the relief or control valve must match the tank’s rating: an over-rated valve on a lower-rated tank is a burst waiting to happen. If supply pressure exceeds the rating, the valve (not luck) is what protects the tank.

Static is the pressure with no water flowing; dynamic is what remains while a faucet runs, after friction losses. A system can show a healthy 60 psi (4 bar) static and still deliver a weak shower if undersized pipework eats the pressure when flow starts — which is why pressure complaints are diagnosed with a gauge under flow.