Home Water Pressure: Testing, Adjusting, and Fixing Low or High Pressure

Testing Your Water Pressure

Screw a pressure gauge onto a hose bib (outdoor faucet) close to where the main water line enters the house. Make sure no other fixtures are running. Read the gauge — this is your static pressure.

Test at different times of day. Municipal water pressure can drop during peak usage (early morning and evening when neighbors are also using water). If your pressure is fine at 2 AM but weak at 7 AM, the issue may be the municipal supply, not your house.

Test at multiple fixtures. If pressure is good at the hose bib but weak at a specific faucet, the problem is in the branch line to that fixture — a clogged aerator, a partially closed valve, or a kinked supply line.

Record the pressure with all fixtures off, then open a faucet and watch the gauge. A large drop (more than 10 PSI) between static and running pressure indicates a restriction somewhere in the system — often a corroded galvanized pipe section, a partially closed valve, or undersized piping.

Pressure-Reducing Valves (PRV)

Most homes connected to a municipal water supply have a pressure-reducing valve (PRV) installed where the main line enters the house. It is a bell-shaped brass fitting with an adjustable bolt on top. The PRV reduces incoming municipal pressure (which can be 80 to 150 PSI or higher) to a safe residential level.

PRVs have a typical lifespan of 7 to 12 years. When they fail, they can either lock at a high setting (dangerously high pressure throughout the house) or restrict to a low setting (weak flow everywhere). A failing PRV sometimes causes inconsistent pressure — fine one day, weak the next.

To adjust a PRV: turn the adjusting bolt clockwise to increase pressure, counterclockwise to decrease. Make small adjustments (quarter turns) and check the gauge after each change. Target 50 to 60 PSI. Do not set it above 80 PSI — this stresses pipes and fixtures and can void the water heater warranty.

If adjusting the bolt has no effect, the PRV needs replacement. This is a straightforward job if you can shut off the water upstream (at the meter or curb stop). Cut out the old PRV and install a new one using compression fittings or solder joints, depending on the pipe material.

Well Water Pressure Systems

Well systems use a pressure tank and a pressure switch to maintain household pressure. The pressure switch turns the pump on at a low setpoint (typically 30 PSI) and off at a high setpoint (typically 50 PSI). This gives you a 30/50 system with an average working pressure of about 40 PSI.

If pressure is consistently low, check the pressure switch settings. The switch has two adjustable nuts: one sets the cut-in pressure (pump turns on), the other adjusts the differential (difference between cut-in and cut-out). Increasing the cut-in pressure by 5 PSI (to a 35/55 system) raises the average household pressure. Check your pump's capacity before going higher — the pump must be able to reach the cut-out pressure.

A waterlogged pressure tank causes the pump to cycle rapidly (on-off-on-off every few seconds). Check the tank's air charge by pressing the Schrader valve on top — it should release air. If water comes out, the bladder has failed and the tank needs replacement. The air precharge should be set 2 PSI below the cut-in pressure.

If the pump runs but pressure does not build, the pump may have lost prime (shallow well jet pumps), the well level may have dropped, or the pump may be worn out. Check the prime first — it is the cheapest fix.

Common Causes of Low Pressure

Partially closed main shutoff valve: the most common and easiest-to-fix cause. Open the valve at the meter and the one where the main line enters the house completely. Gate valves (the round-handle type) must be fully open — even one turn from fully open can restrict flow significantly.

Corroded galvanized pipe: homes with galvanized steel water supply lines (common in homes built before 1960) lose flow capacity as mineral deposits build up inside the pipe. The pipe looks fine from the outside but the inside diameter has narrowed to a fraction of its original size. The fix is repiping — usually with PEX or copper.

Clogged aerators and filters: unscrew faucet aerators and showerheads and check for sediment. Whole-house water filters that have not been changed restrict flow. If cleaning the aerator restores pressure at that fixture, the aerator was the issue.

Municipal supply issues: construction on the water main, a fire hydrant in use nearby, or a main break can temporarily reduce pressure. Call your water utility if pressure drops suddenly and affects the entire house.

High Pressure and Water Hammer

Pressure above 80 PSI stresses every fitting, valve, and appliance in the system. It wears out washing machine solenoids, dishwasher valves, ice maker lines, and toilet fill valves prematurely. It also wastes water — a faucet at 80 PSI flows roughly 50 percent more water than the same faucet at 50 PSI.

Water hammer is a banging sound when a valve closes suddenly (like a washing machine solenoid valve). The momentum of the moving water creates a pressure spike that slams into the closed valve. High system pressure makes water hammer worse because the water moves faster.

Fix water hammer by installing water hammer arrestors at the affected fixtures. These are sealed air chambers that absorb the pressure spike. They screw onto the supply line at the washer hookup or the affected faucet supply. Reducing overall system pressure with the PRV also helps.

A thermal expansion tank on the water heater is required in any system with a PRV or check valve. Without it, the water heater heats water, the water expands, and with no path back to the street (the PRV and check valve block backflow), pressure spikes to dangerous levels. The expansion tank absorbs this excess volume.

Frequently Asked Questions