Low water pressure in the house

What people usually report

A weak shower, a slow-filling toilet tank, or a faucet that trickles. Some notice it only on the hot side, some only upstairs, and some all at once after a repair, a water softener install, or work on the street.

What official sources say the causes can include

• A failed or misadjusted pressure reducing valve (PRV). If every fixture is low and the home has a PRV, check that it is set correctly and working. A failed PRV greatly reduces pressure. Most are bell-shaped and sit on the main line between the meter and the house (City of Bremerton, WA, Public Works).
• A partly closed valve. A main shutoff that is not fully open restricts flow (City of Bremerton, WA, Public Works; City of Phoenix Water Services).
• Clogged aerators. When only some faucets are weak, look for rust, debris, or scale in the aerator screens (City of Bremerton, WA, Public Works; City of Phoenix Water Services).
• The water heater. Low pressure on the hot side only can mean a water heater problem; check that its shutoff valve is fully open (City of Bremerton, WA, Public Works).
• Galvanized pipe and water softeners. Phoenix lists mineral buildup in galvanized plumbing and a softener in need of maintenance (City of Phoenix Water Services). Bremerton adds point-of-use filters and softeners as restrictions (City of Bremerton, WA, Public Works). USGS notes that scale from hard water builds up inside pipes over time, narrowing them and reducing flow and pressure (U.S. Geological Survey).
• A leak on the property. Bremerton lists an on-site leak as a cause (City of Bremerton, WA, Public Works). EPA’s two-hour meter check (U.S. EPA WaterSense) is a simple way to look for one: see high water bill, no visible leak.
• Elevation and local work. Pressure drops 0.433 psi for every foot of elevation, so higher homes see lower pressure (City of Bremerton, WA, Public Works). Construction on the water system can lower pressure for a time (City of Phoenix Water Services).

What the numbers mean

Utilities set their own ranges. Phoenix calls 40 to 100 psi acceptable (City of Phoenix Water Services). Bremerton’s system runs from about 30 psi to over 100 psi at the meter, treats under 30 psi as low, and suggests a PRV above 80 psi, noting that under the Uniform Plumbing Code owners are responsible for a PRV when static pressure exceeds 80 psi (City of Bremerton, WA, Public Works). Cobb County expects properties to keep pressure at or below 80 psi (Cobb County Water System, GA). Your own utility’s figure is the one that applies.

How to find out

1. One fixture or all? Check several faucets, hot and cold. One weak fixture points to its aerator or cartridge.
2. Ask a neighbor. If theirs dropped too, call the utility.
3. Measure it. A pressure gauge that attaches to an outside faucet or hose bib gives you a reading (City of Bremerton, WA, Public Works). Cobb County notes the PRV usually sits after the front spigot, so a front reading can be higher than the back (Cobb County Water System, GA).
4. Check the valves. Main shutoff and water heater valves fully open (City of Bremerton, WA, Public Works).
5. Leave the PRV to a pro. Bremerton says PRVs should be adjusted by a licensed plumber (City of Bremerton, WA, Public Works).

Some utilities will send a technician to read the pressure at your meter; Bremerton offers this (City of Bremerton, WA, Public Works). Our note on low pressure when hiring a plumber covers what to ask for.