How to Adjust the PSI on a Water Pressure-Reducing Valve

Screw the water pressure gauge clockwise onto the hose bib on the exterior of your home closest to the water pressure-reducing valve until it is snug. Turn on the faucet. When the needle stops on the gauge, make note of the reading.

Remove the lid to the water supply valve box. The pressure-reducing valve usually is in a valve box inset into the ground between the house and the water meter from the water agency. The lid has a small hole on one end to insert your finger or a tool to lift the ground-level lid from it.

Loosen the locknut atop the water pressure-reducing valve by unscrewing it with the crescent wrench or open-end wrench sized to fit it. The locknut is closest to the regulating valve's body. Only loosen it a couple of turns to free the bolt or screw that allows you to adjust the water pressure.

Slide an open-end wrench, or socket and ratchet onto the top bolt onto which the locknut is threaded. If the bolt has a slot in it to accept a flat-head screwdriver, use a screwdriver instead. Loosen the bolt counterclockwise to reduce pressure, and clockwise to increase it. Make adjustments in half or quarter turns only. Make the first adjustment, then check the water pressure gauge reading, or have someone tell you the reading if the gauge is not installed nearby.

Tighten the locknut back into position after you make your final adjustment. You might need to hold the bolt in place with the screwdriver or wrench to ensure it doesn't move as you tighten the locknut.

Turn the faucet off that has the water pressure gauge on it. Remove the gauge from the hose bib or faucet.