Setting a Pressure Reducing Valve: Shut Down, Swap, Set, and Test

A pressure reducing valve that is set wrong can stress fixtures and appliances, so the swap follows a clear order of shutting down, removing, installing, setting, testing, and recording the result.

A pressure reducing valve sits on the main water line and lowers the pressure that enters the house. When it fails or is replaced, the new unit has to be installed in the right direction and set to the right pressure. The steps below follow the order that keeps a small job from becoming a flood or a fixture problem. If your home has no existing valve, or the water heater has no expansion control, a plumber should look at the layout first.

Before you start

Find the valve and read its arrow, which shows the direction of flow. Note the existing setting if the old valve has a dial or a marked adjustment. Locate the main shutoff, and know whether the line has a bypass. Gather a bucket, towels, a pipe wrench, a pressure gauge that fits a hose bib, and the replacement valve with its instructions. Keep the instructions with the house records.

Shut down and remove

Close the main shutoff. Open a faucet at the lowest point and a faucet upstairs to drain the line. Place the bucket under the old valve. Loosen the unions or fittings and remove the old unit, noting how it was oriented.

Install the new valve

Fit the new valve so its arrow points the same way as the flow. Use the sealant or washers the manufacturer specifies, and tighten the fittings in the order the instructions show. Do not overtighten plastic or soft fittings.

Open slowly and check for leaks

Open the main shutoff slowly and watch each joint. Let the line fill and look for drips or weeping at every connection before you move on.

Set the pressure

Attach the gauge to a hose bib close to the valve, read the current pressure, and adjust the valve's screw or dial in small steps. Use the setting the valve maker or your plumber specifies for your home, not a number from memory. Recheck the gauge at a fixture farther from the valve, since the reading can change along the line.

Test and record

Run a faucet, flush a toilet, and run a washing machine if you can. Listen for banging in the pipes and watch for fixtures that sputter. Write down the valve model, the setting, the gauge reading, and the date of the work in your house records so the next visit starts with facts.