How to Install a Pressure Reducing Valve (PRV)
Updated March 2, 2026
Install or replace a PRV on the main supply line to reduce high water pressure below 80 PSI -- protecting pipes, fixtures, and appliances from pressure damage.
Overview
Municipal water pressure above 80 PSI damages plumbing over time. Supply lines develop pinhole leaks. Faucet cartridges fail prematurely. Washing machine and dishwasher solenoid valves burn out. Toilet fill valves run constantly. Water hammer gets louder. A pressure reducing valve (PRV) on the main supply line brings 80-150 PSI street pressure down to a safe 50-60 PSI inside the house. Most homes built after 1990 already have one. If yours has failed (pressure creeps above 80 PSI) or was never installed, adding one protects every fixture and appliance in the house.
What You'll Need
Safety First
- Turn off water at the street meter before installing a PRV on the main line. The PRV installs between the meter and the house.
- High water pressure (above 80 PSI) is a code violation in most jurisdictions. If your pressure exceeds 80 PSI, a PRV is required.
- A PRV creates a closed system -- water cannot push back to the street. Install an expansion tank on the water heater to absorb thermal expansion. Without it, the T&P valve will discharge during heating cycles.
Step-by-Step Instructions
- Test Your Current Pressure
Screw a pressure gauge ($10-$15) onto an outdoor hose bib. Turn it on fully. Read the gauge. Below 60 PSI: you probably do not need a PRV (unless it fluctuates wildly). 60-80 PSI: acceptable, but a PRV set to 55 PSI provides a safety margin. Above 80 PSI: a PRV is needed. Also check: does your house already have a PRV? Look on the main supply line near where it enters the house -- a bell-shaped brass body with an adjustment bolt on top is a PRV. If it exists but pressure is high, it has failed and needs replacement.
Tip: Test pressure at multiple times of day. Municipal pressure fluctuates -- it is highest at night when demand is low and lowest during peak morning and evening use. If pressure exceeds 80 PSI at any time, install the PRV. - Choose the PRV
Residential PRVs come in 3/4-inch and 1-inch sizes to match the main supply line. Watts LF25AUB ($30-$50) and ZurnWilkins NR3XL ($40-$70) are the two most common residential models. Both are adjustable from 25-75 PSI and have a factory pre-set of 50 PSI. Choose the size that matches your main line -- most homes are 3/4-inch. If you are replacing an existing PRV, match the size and connection type (threaded, solder, or push-fit).
Tip: The Watts LF25AUB-Z3 comes with a built-in strainer that catches sediment before it reaches the valve seat. This extends the PRV life by 30-50% in areas with hard water or sandy well water. - Install the PRV
Turn off water at the street meter. Open a faucet to drain residual pressure. Cut the main supply line at the installation point (after the main shut-off valve, before any branch lines). Install the PRV with the flow direction arrow pointing toward the house (inlet on the street side, outlet on the house side). Use threaded connections with Teflon tape, solder connections, or SharkBite push-fit. Install a pressure gauge on the house side of the PRV to monitor output. Install an expansion tank on the cold water inlet to the water heater (the PRV creates a closed system that needs thermal expansion relief).
Tip: If replacing an old PRV, the connections are already in place. Unscrew the old one, clean the threads, and thread the new one in. Use two wrenches -- one holding the pipe, one turning the PRV -- to avoid twisting the supply line. - Set the Pressure and Test
Turn on the water at the street meter. The PRV reduces incoming pressure to the factory pre-set (usually 50 PSI). Read the downstream pressure gauge. Adjust if needed: the bolt on top of the PRV turns with a wrench -- clockwise increases pressure, counterclockwise decreases. Target: 50-60 PSI. Open faucets throughout the house and verify consistent pressure. Flush toilets -- they should fill at a normal rate without banging or excessive flow noise. Check all new connections for leaks under full pressure.
Tip: Set the PRV to 55 PSI as a starting point. This provides adequate flow for all fixtures while staying well below the 80 PSI threshold. If the second-floor shower feels weak, increase to 60 PSI. Do not exceed 70 PSI.
Pro Tips
- PRVs have a lifespan of 7-12 years. If your existing PRV is older than 10 years and pressure has crept up, replace it rather than adjusting. The internal spring and diaphragm wear out and adjustment only buys temporary relief.
- A failed PRV is the number one cause of unexplained high water pressure in homes that previously had normal pressure. If your water pressure gradually increased over months or years, the PRV is failing.
- The expansion tank is not optional when a PRV is installed. The PRV blocks water from pushing back to the street, creating a closed system. When the water heater heats water, it expands. Without an expansion tank, the pressure spikes above the PRV set point and the T&P valve opens. A $40-$80 expansion tank prevents this.
- Some municipalities install a PRV at the meter (street-side). Check before installing one in the house -- you may already have one. Two PRVs in series can cause excessively low pressure.
- If your house is on a hill above the street level, the static pressure may already be low (each foot of elevation above the street reduces pressure by 0.43 PSI). A house 50 feet above the street loses 21 PSI from elevation alone. You may not need a PRV -- you may need a booster pump.
When to Call a Pro
Call a plumber if you are not comfortable working on the main supply line, if the existing PRV is soldered in and you do not have soldering skills, if you need an expansion tank installed on the water heater at the same time, or if you suspect the high pressure is caused by a thermal expansion issue rather than high street pressure (requires diagnosis).
Frequently Asked Questions
When should I call a plumber to install a pressure reducing valve (prv)?
Call a plumber if you are not comfortable working on the main supply line, if the existing PRV is soldered in and you do not have soldering skills, if you need an expansion tank installed on the water heater at the same time, or if you suspect the high pressure is caused by a thermal expansion issue rather than high street pressure (requires diagnosis).
What are some expert tips to install a pressure reducing valve (prv)?
PRVs have a lifespan of 7-12 years. If your existing PRV is older than 10 years and pressure has crept up, replace it rather than adjusting. The internal spring and diaphragm wear out and adjustment only buys temporary relief. A failed PRV is the number one cause of unexplained high water pressure in homes that previously had normal pressure. If your water pressure gradually increased over months or years, the PRV is failing. The expansion tank is not optional when a PRV is installed. The PRV blocks water from pushing back to the street, creating a closed system. When the water heater heats water, it expands. Without an expansion tank, the pressure spikes above the PRV set point and the T&P valve opens. A $40-$80 expansion tank prevents this. Some municipalities install a PRV at the meter (street-side). Check before installing one in the house -- you may already have one. Two PRVs in series can cause excessively low pressure. If your house is on a hill above the street level, the static pressure may already be low (each foot of elevation above the street reduces pressure by 0.43 PSI). A house 50 feet above the street loses 21 PSI from elevation alone. You may not need a PRV -- you may need a booster pump.
What tools do I need to install a pressure reducing valve (prv)?
You will need: Pressure reducing valve ($30-$80, sized to match main line), Pressure gauge ($10-$15, for monitoring output), Expansion tank ($40-$80, required for the water heater when a PRV creates a closed system), Tube cutter (for copper) or pipe wrenches (for threaded connections), Teflon tape (for threaded connections), Adjustable wrench (for PRV adjustment bolt), Meter key ($10-$15, for street meter shut-off).
When should I call a professional instead of doing this myself?
Call a plumber if you are not comfortable working on the main supply line, if the existing PRV is soldered in and you do not have soldering skills, if you need an expansion tank installed on the water heater at the same time, or if you suspect the high pressure is caused by a thermal expansion issue rather than high street pressure (requires diagnosis).
How difficult is this project?
This project is rated intermediate. It requires moderate DIY skill and the right tools.
How long does this take?
Plan for approximately 1 - 2 hours. First-timers may need extra time.
How much will this cost?
The estimated cost is $30 - $80 for the valve; $150 - $350 for a plumber. Costs vary by location and materials chosen.