Pipes and pressure
Low Water Pressure: Causes and Fixes
Updated · By the Keystream Plumbing editorial team · How we research
Start by narrowing it down
Two questions do most of the work: is it one fixture or all of them, and is it hot water only or both hot and cold?
- One fixture, hot and cold: clogged aerator, showerhead or cartridge at that fixture
- Hot only, everywhere: sediment in the water heater or a partly closed valve on the heater
- Everything, suddenly: a valve that was left partly closed, a failed pressure regulator, a leak or a utility problem
- Everything, gradually over years: pipes narrowing with corrosion or scale
Measure it
A pressure gauge that threads onto a hose bib costs a few dollars. With no water running, 40 to 80 psi is the normal range for a home. Below about 40 psi, showers feel weak; above 80 psi, pressure is hard on hoses, valves and water heaters and most codes call for a regulator.
Fixes you can do
Unscrew the aerator or showerhead and rinse or soak it in vinegar to dissolve mineral buildup. Make sure the main shutoff and the valve at the meter are fully open; a gate valve that is partly closed, or one whose gate has broken off inside, restricts the whole house. If you have a water softener or whole-house filter, put it in bypass to see whether it is the restriction.
The pressure-reducing valve
Many homes have a bell-shaped pressure-reducing valve (PRV) where the main enters. They wear out after 10 to 15 years and can fail low, starving the house, or fail high. A gauge reading that is low at the hose bib but normal at the utility side points to the PRV, which a plumber replaces.
Old pipes
Galvanized steel pipe, common in homes built before the 1960s, rusts from the inside until the opening is a fraction of its original size. Pressure may measure fine with nothing running but collapse when two fixtures are used at once. Cleaning does not fix it; repiping does.
Leaks and the utility
A leak in the service line or under a slab diverts water before it reaches your fixtures. Do the meter test: with everything off, the meter should not move. If your neighbors have low pressure too, call the water utility, since a main break or work on the system may be the cause.
Frequently asked questions
What is normal water pressure for a house?
Between 40 and 80 psi. Many plumbers aim for roughly 50 to 60 psi. Pressure above 80 psi generally requires a pressure-reducing valve under plumbing codes.
Why is my water pressure low only when two things are running?
The pipes or the regulator cannot supply enough flow. Corroded galvanized pipe, an undersized or failing pressure regulator, or a partly closed valve are the usual reasons.
Can a water softener cause low pressure?
Yes. A clogged resin bed or an undersized softener restricts flow. Put the softener in bypass; if pressure returns, the softener needs service.
Editorial note: This guide is general information for homeowners, not a substitute for an on-site assessment. Local codes and conditions vary; a licensed pro can confirm what applies to your home. See our editorial policy.
