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Low Water Pressure Through the Whole House

If every fixture in the house is weak, the problem is almost never inside the walls. It is on the supply side, and there are only about six things it can be.

Water meter in a ground chamber with the lid lifted, brass valve alongside

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Start by confirming it really is the whole house. Run the kitchen tap, then a bathroom tap at the other end of the property, then an outside tap if you have one. If all three are weak, read on. If one is weak and the others are fine, that is a different and far simpler problem.

Normal residential supply sits at roughly 45–80 psi, and anything below 40 psi is genuinely low. Normal and low ranges as published by Grundfos in its homeowner guide to low water pressure. Measuring it takes about a minute and turns this from a guess into a number.

The six causes, in the order worth checking

1. A main shut-off or meter valve left part-closed

The simplest possible answer, and worth eliminating first. After any plumbing work, a valve sometimes goes back most of the way open rather than all of the way. A gate valve that looks open can still be throttling flow. How to check both valves.

2. The pressure-reducing valve

If your street pressure is high, a PRV sits just inside the property to bring it down. They drift and they fail, usually gradually. Life expectancy is commonly 10 to 15 years, and it is the property owner's device to maintain, not the utility's. Life expectancy and responsibility as published by the Elizabethton, Tennessee water utility. A PRV that has drifted low is an adjustment; one that has failed is a replacement. More on identifying and adjusting one.

A lever ball valve and a wheel-handled gate valve on the same run of pipe

3. Galvanized supply pipe closing up

In older housing the supply pipe itself is the constriction. Galvanized steel corrodes from the inside, and the bore narrows over decades until a half-inch line is passing far less than it was built to. The tell is that the loss is gradual and it is worst at the fixtures furthest from where the water enters. How to identify galvanized pipe.

4. A leak between the meter and the house

Water leaving the system before it reaches you shows up as pressure loss and as a meter that creeps with every tap shut. Turn everything off, note the meter, wait an hour and look again. Movement means a leak, and an underground one on the property side is the owner's to fix.

5. The municipal supply, or a well pressure tank

If the whole street is affected, it is not your plumbing. Ask a neighbor. On a private well the equivalent is the pressure tank: when its bladder fails, pressure swings and the pump short-cycles rather than holding steady.

Wall-mounted pipework carrying two pressure gauges side by side

6. Simultaneous demand

If pressure is fine alone and collapses when two fixtures run, the supply is adequate but the delivery is restricted — usually pipe diameter or a partly closed valve rather than pressure as such. That pattern has its own page.

What to have ready if you call

A contractor can work faster with four things: the reading from your gauge, whether it is the whole house or one fixture, roughly when the house was built, and whether the change was sudden or gradual. Sudden points at a valve or a leak. Gradual points at the pipe.