What are expert tips for installing a pressure reducing valve?

Install a pressure gauge permanently on the downstream side so you can monitor pressure over time. PRVs can drift or fail, and a gauge tells you immediately. Set the pressure to 50-60 PSI. Lower than 40 and you'll notice weak flow at fixtures. Higher than 70 and you're not getting the full protection benefit. If you also have a thermal expansion tank on the water heater, check that it's set to match the PRV output pressure. A PRV creates a closed system, and thermal expansion needs somewhere to go.

What mistakes should I avoid with installing a pressure reducing valve?

Installing the PRV backwards -- water won't flow properly and the valve can't regulate. Not installing union fittings, making future maintenance require cutting pipe. Not accounting for thermal expansion. A PRV creates a closed system, so you need an expansion tank on the water heater. Setting the pressure too low and wondering why the upstairs shower has no pressure.

Installing a Pressure Reducing Valve | The Plumbing Directory

Overview

High water pressure feels great in the shower, but it's quietly destroying your plumbing. Pressure above 80 PSI stresses pipes, joints, water heaters, and appliances. It causes pinhole leaks, blown washing machine hoses, and premature failure of faucet cartridges and toilet fill valves. A pressure reducing valve (PRV) installed on the main supply line brings the pressure down to a safe 50-60 PSI. It's a $50-$100 part that can prevent thousands in damage.

What to Know

Do You Need One?

Test your water pressure with a $10 gauge from any hardware store -- thread it onto a hose bib and turn on the water. If it reads above 80 PSI, you need a PRV. Municipal water pressure varies wildly by location and time of day. We regularly see homes with 100-120 PSI that have no PRV. That's a ticking time bomb.

Where It Goes

The PRV installs on the main water supply line, right after the main shutoff valve and before it branches out to fixtures. Typically in the basement, crawl space, or utility room near the water meter. The goal is to reduce pressure for the entire house in one spot.

Sizing

Residential PRVs are usually 3/4-inch for most homes. If you have a 1-inch main supply, get a 1-inch PRV. Undersizing restricts flow. The valve should be rated for at least the maximum incoming pressure your system might see.

Tools & Materials

Pressure reducing valve (correct pipe size)
Pipe wrenches or adjustable wrenches
Pipe cutter
Thread seal tape or pipe dope
Union fittings (for future removal)
Pressure gauge

Step by Step

Shut off the main water
Close the main shutoff valve at the meter. Open a faucet to drain pressure. Place a bucket under the work area -- cutting the pipe will release residual water.
Cut the pipe and prep
Mark the section of pipe where the PRV will be installed. Cut the pipe with a pipe cutter. Clean and deburr the cut ends. If using threaded connections, thread male adapters onto the pipe ends.
Install union fittings
Install union fittings on both sides of the PRV. Unions allow you to remove the PRV in the future for maintenance or replacement without cutting pipe. This is a small extra cost that pays off in 10 years when the valve needs service.
Install the PRV
Thread the PRV into the union fittings. The arrow on the valve body must point in the direction of water flow (from the street side toward the house). Wrap all threaded connections with tape or pipe dope.
Set the pressure and test
Turn the main water back on slowly. Use the adjustment screw on the PRV to set the output pressure -- typically 50-60 PSI. Clockwise increases pressure, counterclockwise decreases. Check with the pressure gauge downstream. Check all connections for leaks.

Pro Tips

Install a pressure gauge permanently on the downstream side so you can monitor pressure over time. PRVs can drift or fail, and a gauge tells you immediately.
Set the pressure to 50-60 PSI. Lower than 40 and you'll notice weak flow at fixtures. Higher than 70 and you're not getting the full protection benefit.
If you also have a thermal expansion tank on the water heater, check that it's set to match the PRV output pressure. A PRV creates a closed system, and thermal expansion needs somewhere to go.

Mistakes to Avoid

Installing the PRV backwards -- water won't flow properly and the valve can't regulate.
Not installing union fittings, making future maintenance require cutting pipe.
Not accounting for thermal expansion. A PRV creates a closed system, so you need an expansion tank on the water heater.
Setting the pressure too low and wondering why the upstairs shower has no pressure.

When to Call a Pro

If your main supply is galvanized steel, if you need to work near the water meter (some jurisdictions require this), or if the pipe size is larger than 1 inch -- call a plumber. Also worth hiring out if you're not comfortable cutting into the main supply line.

Bottom Line

A PRV is a $50-$100 investment that protects every fixture and appliance in your house. If your pressure is above 80 PSI, this should be priority number one. Install with union fittings for easy future service, and don't forget the thermal expansion tank.

Installing a Pressure Reducing Valve