How to Adjust a Water Pressure Reducing Valve (PRV)

Before making any adjustments, you must establish a baseline pressure reading. Locate an outdoor hose bibb or a utility sink faucet. Ensure all other faucets and water-using appliances in the home are turned off to get a static pressure reading. Firmly screw the water pressure gauge onto the faucet's threads. Open the faucet's handle completely. Observe the dial on the gauge and note the pressure reading in PSI (pounds per square inch). The ideal residential pressure is between 50 and 60 PSI.

Locate the PRV, which is typically a bell-shaped brass valve installed on the main water line shortly after the main shutoff valve and water meter. On the top of the 'bell' is the adjustment mechanism, which consists of a long threaded bolt and a locknut that secures it. To allow for adjustment, you must first loosen this locknut. Place one adjustable wrench on the locknut and another on the adjustment bolt head above it to hold it steady. Turn the wrench on the locknut counter-clockwise about one full turn. This should be enough to allow the adjustment bolt to turn freely.

With the locknut loose, you can now change the pressure setting. To INCREASE pressure, use a wrench to turn the adjustment bolt clockwise (screwing it down). To DECREASE pressure, turn the bolt counter-clockwise (unscrewing it). It is crucial to make these adjustments in small increments, such as a quarter-turn at a time, to prevent drastic changes that could overshoot your target.

After making a small adjustment, the pressure in the pipes needs to stabilize to reflect the new setting. To do this, go to any faucet in the house (other than the one your gauge is attached to) and turn it on for 20-30 seconds. This action relieves the static pressure and allows the PRV to settle at its new set point. After running the water, turn the faucet off completely. Return to your water pressure gauge to read the new, adjusted pressure.

Compare your latest pressure reading with your target of 50-60 PSI. It is unlikely you will hit the exact number on the first try. You will need to repeat the adjustment and testing cycle. If the pressure is still too high, turn the adjustment bolt another quarter-turn counter-clockwise. If it's too low, turn it a quarter-turn clockwise. After each adjustment, remember to run a faucet to stabilize the system before taking a new reading. Continue this iterative process until the gauge shows a stable pressure within the desired range.

Once the water pressure is consistently holding within your target range, you must lock the adjustment in place to prevent it from changing over time due to vibrations. Use one wrench to hold the adjustment bolt head firmly in its final position. With your other wrench, turn the locknut clockwise until it is snug against the body of the PRV. It should be firm, but do not overtighten, as this can strip the threads or damage the valve.

As a final quality check, look at the pressure gauge one last time after the locknut has been tightened. The act of tightening the nut can sometimes cause the adjustment bolt to turn slightly, which may alter the pressure. If the reading is still correct, your job is done. You can now unscrew the water pressure gauge from the faucet. If the pressure has shifted outside your target range, you will need to loosen the locknut and make one final micro-adjustment.