How to Adjust a Water Pressure Reducing Valve (PRV)

Before beginning, ensure you have all the necessary tools. This prevents interruptions during the process. You will need a water pressure gauge to measure the pressure, an adjustable wrench to handle the locknut, and a flathead screwdriver for the adjustment screw. Check that your pressure gauge is in good working order and that its threads are clean.

To get an accurate baseline, you must test the system's static pressure. First, ensure no water is running anywhere in the house—turn off all faucets, and make sure appliances like washing machines or dishwashers are not in use. Locate an outdoor hose bib or the cold water connection for your washing machine. Screw the water pressure gauge tightly onto the threads by hand. Open the faucet or valve fully. The needle on the gauge will jump up and settle on the current static pressure reading. Note this number. A typical residential pressure should be between 40-80 PSI.

Locate the water pressure reducing valve. It is a brass, bell-shaped device installed on the main water line, typically just after the main shutoff valve and water meter. On top of the 'bell' housing, you will find the adjustment mechanism, which consists of a long threaded screw (the adjustment screw) and a nut at its base (the locknut). Using your adjustable wrench, turn the locknut counter-clockwise to loosen it. You only need to loosen it a few turns to allow the adjustment screw to move freely.

With the locknut loose, you can now adjust the pressure. Use a flathead screwdriver to turn the adjustment screw. To DECREASE the pressure (as per our assumed goal), turn the screw COUNTER-CLOCKWISE. To INCREASE the pressure, you would turn it CLOCKWISE. Make only a small adjustment, such as a one-quarter to one-half turn, at a time. This prevents drastic changes and allows for fine-tuning.

After making an adjustment, you need to test the new pressure setting. Go to a faucet inside or outside the house (it can be the same one the gauge is on) and open it for 15-30 seconds. This allows the water to flow, equalizing the pressure in the system to the new setting on the PRV. Close the faucet and check the reading on your water pressure gauge. If the pressure is still too high or you've gone too low, repeat Step 4 and this step until you achieve your desired pressure. The ideal range for most homes is 50-60 PSI.

Once you have successfully set the water pressure to your desired level (50-60 PSI), you must lock in the setting. Use the flathead screwdriver to hold the adjustment screw perfectly still so it doesn't turn. While holding it, use the adjustable wrench to tighten the locknut by turning it CLOCKWISE until it is snug against the bell housing of the valve. Do not over-tighten, but ensure it is secure enough to prevent the adjustment screw from vibrating or moving over time. Once tightened, remove the pressure gauge and close the faucet.