Water pressure that is too high is one of those problems that goes unnoticed until it causes another one. A pressure reducing valve (PRV) is the part that protects your plumbing from it. This guide explains what a PRV does, how to check whether yours is working, and when to call a plumber.
What a PRV does
The water in the main under the street is at a higher pressure than your house needs. The Pacific Northwest National Laboratory's Building America Solution Center notes that supply mains can exceed 200 psi because utilities use pumps to boost pressure. A PRV is installed on the water line where it enters your house and reduces that pressure to a level that is safe for your pipes, fixtures and appliances.
Most plumbing codes require a PRV where the pressure goes above 80 psi, because higher pressure can rupture pipes and damage fixtures. The same source says a stricter limit of 60 psi is used for new construction in energy-efficiency programs. In practice, many plumbers aim to keep household pressure somewhere in the 50 to 60 psi range, which is high enough to give a good shower and low enough to be easy on the plumbing. Local code amendments vary, so ask your building department if you need an exact figure for your address.
The most common type is a direct-acting valve: a bell-shaped brass body on the main line, just past the main shutoff. Many older homes do not have one.
Signs your pressure is too high
- Pipes that bang or hammer when a tap or an appliance valve closes.
- Faucets and toilets that drip, run on, or wear out quickly.
- Showerheads and aerators that spray in a hard stream.
- A water heater relief valve that drips.
- Water bills that creep up because of small leaks.
- Appliance hoses and supply lines that fail early.
None of these proves that pressure is the cause. A gauge does.
How to measure your pressure
A water pressure gauge with a hose-thread fitting costs a few dollars at a hardware store.
1. Turn off all water use in the house, including the ice maker and the washer. 2. Screw the gauge onto an outdoor hose bib or a laundry-sink faucet with a hose thread. 3. Open the tap fully and read the gauge. 4. Check it again at night and early in the morning. A reading that rises when nobody is using water suggests a failing PRV, because when the valve fails it can let the street pressure creep through.
If the reading is above 80 psi, a PRV is called for. If it is between 60 and 80 psi and you have symptoms, discuss it with a plumber. If you have a PRV and the pressure is higher than it was, the valve is a suspect.
Signs your PRV is failing
- Pressure higher than it was, or pressure that changes through the day.
- A visible leak at the valve body.
- Banging pipes that started recently.
- A dripping water heater relief valve.
A PRV is a mechanical part with a diaphragm and a spring, and it wears out. Replacing it before it fails completely is cheaper than the damage a failure can cause.
One more thing: thermal expansion
A PRV makes your plumbing a closed system, meaning water cannot flow back toward the street. The Building America Solution Center notes that this means thermal expansion can lead to increased pressure in some cases, and says local codes should guide how that is handled. When water in the heater warms it expands, and with nowhere to go the pressure climbs. A small expansion tank on the water heater is the usual answer. If the relief valve on your heater drips after a PRV was installed, ask whether an expansion tank is needed.
What about low pressure?
A PRV set too low, or one that is failing, can cause low pressure at every tap. But other causes are more common: a partly closed valve, a clogged fixture screen, a leaking or corroded service line, or a problem on the utility's side. If you suspect a leak, EPA's WaterSense program suggests reading your meter before and after a two-hour period when no water is being used. If the meter changes at all, you probably have a leak. A toilet leak is the most common: a few drops of food coloring in the tank that show up in the bowl after ten minutes mean a leak.
EPA says that the average household wastes more than 9,300 gallons a year to leaks, and that fixing easy leaks can save about 10 percent on a water bill. High pressure makes leaks worse.
Do it yourself or call a pro
Measuring pressure is a DIY job. Adjusting or replacing a PRV is not a beginner task. It involves shutting off the water to the whole house, cutting into the main line, and possibly adding an expansion tank. Many PRVs have an adjustment screw, but adjusting it without a gauge can leave you with pressure that is too high or too low.
If your pressure reads above 80 psi, or you have a PRV that seems to be failing, call a plumber. Measure first and tell them the reading.
This guide was last reviewed on October 15, 2026.