PSI (Pounds per Square Inch)
The standard unit for measuring water pressure, where residential plumbing typically targets 40 to 60 PSI and code limits incoming pressure to 80 PSI.
PSI describes how hard water is pushing against the inside of your pipes. A simple gauge that threads onto an outdoor spigot or the laundry valve reads it directly, and that ten-dollar tool settles most pressure arguments in under a minute. If the needle sits between 40 and 60, the supply side is healthy. A reading under 40 explains weak fixtures; a reading over 80 is a warning sign that something upstream, usually a pressure reducing valve, has failed or was never installed.
High PSI does more quiet damage than low PSI. Sustained pressure above 80 shortens the life of faucet cartridges, toilet fill valves, water heater tanks, dishwasher and washing machine inlet valves, and the rubber supply hoses behind them. It is also the most common driver of water hammer, the bang you hear when a valve slams shut. Because the harm accumulates over months, many homeowners run dangerously high pressure for years without realizing it until a hose bursts.
A gauge reading is a snapshot, so timing matters. City pressure often climbs overnight when demand drops, so a meter that reads 70 PSI at dinner can read 95 at 3 a.m. A gauge with a lazy hand, which records the peak, tells the fuller story. That overnight spike is exactly when burst supply lines flood a house, which is why plumbers care about the maximum rather than the average.
Talking to a contractor about this?
Run the project past a licensed plumbing pro first. Calls are answered around the clock and routed to a pro serving your area.
- Main Shutoff Valve : The valve that stops all water entering the house, typically located where the supply line comes through the wall near the meter or in the basement.
- Water Meter : The utility-owned device that measures how much water your home uses, usually located at the property line in a buried box or in the basement.
- GPM (Gallons Per Minute) : A measure of flow rate, the volume of water a fixture or system delivers each minute, distinct from pressure, which is the force behind it.
- Angle Stop / Fixture Shutoff : The small individual shutoff valve under a sink or behind a toilet that stops water to that one fixture without shutting down the whole house.