How to adjust a Watts pressure reducing valve
A Watts pressure reducing valve (PRV) has an adjustment screw on top that you turn to raise or lower the water pressure in your home. The screw is usually a hex bolt or a slot-head screw under a plastic cap. Turning it clockwise increases pressure; counterclockwise decreases it. You adjust it while water is running through the valve, and the change takes effect when ready.
Before you start, buy a pressure gauge that screws onto a hose bib (outdoor faucet) — they cost $10 to $20 at any hardware store. You need this to see what pressure you are actually setting, because guessing by feel leads to either low pressure at your showers or damage to appliances and pipes.
Key Takeaways
- Watts PRVs have an adjustment screw on the bonnet (the cap on top) that you turn with a wrench or screwdriver while water flows through the valve.
- You must use a pressure gauge screwed onto an outdoor faucet to read the actual pressure — you cannot adjust safely by feel alone.
- Most homes need pressure between 50 and 80 pounds per square inch (psi); check your water bill or call your water provider to learn your incoming pressure.
- If the valve will not hold pressure after adjustment, the internal seat may be worn and the valve may need replacement rather than adjustment.
- Adjustments take effect when ready, so turn the screw slowly in small quarter-turn increments and check the gauge after each one.
What pressure your home should have
Most municipal water systems deliver water at 60 to 80 psi. If your incoming pressure is above 80 psi, a PRV protects your pipes, water heater, and appliances by stepping it down to a safer level. If it is below 60 psi, you may not need a PRV at all, or you may want to adjust it higher so showers and washing machines work properly.
Call your water provider and ask what pressure they deliver to your meter. Write that number down. Then use your pressure gauge to measure the pressure at an outdoor faucet with the PRV in place. The difference tells you how much the valve is reducing. If your provider delivers 85 psi and your gauge reads 65 psi, the valve is doing its job — it is cutting 20 psi.
If you want to change the pressure, aim for somewhere between 50 and 80 psi at your hose bibs. Below 50 psi, toilets fill slowly and showers weaken. Above 80 psi, you risk leaks in supply lines, damage to water heater dip tubes, and premature failure of washing machine inlet valves.
Tools and materials you will need
Gather these items before you start: a pressure gauge with a hose-bib fitting (the kind that screws onto an outdoor faucet), an adjustable wrench or the correct hex key for your valve's adjustment screw, a flathead screwdriver if the screw is slot-head, and a bucket or towel to catch any water that drips when you remove the gauge.
The adjustment screw on a Watts PRV is usually a 1/4-inch or 3/8-inch hex bolt, or sometimes a slotted screw. Check your valve's model number on the body — you can look it up online or call a plumber to confirm which tool fits. Using the wrong size can strip the screw and make the valve impossible to adjust.
Step-by-step adjustment process
First, turn on a faucet inside the house so water is flowing through the PRV. This is important: the valve adjusts under load, and you need water moving through it for the adjustment to take effect correctly.
Screw your pressure gauge onto the nearest outdoor faucet. Turn the faucet on fully and read the gauge. Write down the number. This is your baseline pressure.
Locate the adjustment screw on top of the PRV bonnet (the cap-shaped part on the valve body). If there is a plastic cap covering it, pry it off gently with a flathead screwdriver. Place your wrench or hex key on the screw.
Turn the screw clockwise in quarter-turn increments to raise pressure, or counterclockwise to lower it. After each quarter turn, wait 10 to 15 seconds, then check the gauge reading at the outdoor faucet. The pressure will climb or drop slowly as the valve adjusts. Stop when the gauge shows the pressure you want.
Once you reach your target pressure, turn off the indoor faucet you opened earlier. The pressure may rise slightly when flow stops — this is normal. Check the gauge one more time with the faucet off to confirm the final pressure is acceptable.
What to do if the valve will not hold pressure
If you turn the adjustment screw all the way clockwise and the pressure still will not rise above a certain point, the internal seat of the valve may be worn or fouled with mineral deposits. This is common in areas with hard water or in older valves.
Try closing the isolation valve upstream of the PRV (if you have one), then opening the PRV's bleed screw to release pressure inside. Let it sit for 15 minutes, then close the bleed screw and reopen the isolation valve. This sometimes clears light mineral buildup. Adjust the screw again and check the pressure.
If pressure still will not rise, the valve's internal diaphragm or seat is likely damaged. At that point, the valve needs replacement rather than adjustment. A new Watts PRV costs $40 to $150 depending on the model, and installation takes a plumber 30 minutes to an hour if the old valve comes out easily.
Common mistakes to avoid
Do not adjust the valve without a pressure gauge. You cannot feel the difference between 60 psi and 75 psi, and guessing can lead to either weak water pressure or damage to your appliances and pipes. The gauge is the only reliable way to know what you have set.
Do not turn the adjustment screw more than a full rotation without checking the gauge. Large adjustments can overshoot your target pressure and make it hard to dial in the exact level you want. Small quarter-turn increments give you control.
Do not assume the PRV is broken if pressure fluctuates slightly throughout the day. Pressure naturally rises when demand is low (early morning, late night) and falls when demand is high (morning showers, laundry day). A swing of 5 to 10 psi is normal. If the swing is wider than that, the valve may have an internal problem.
When to call a plumber
Call a plumber if the adjustment screw is stuck or stripped and will not turn. Forcing it can break the bonnet and require valve replacement. If you have adjusted the screw but pressure still will not stay where you set it, the valve's internal parts are worn and replacement is the right fix.
Also call a plumber if you are not sure where your PRV is located, or if you cannot find the adjustment screw. Some older Watts models have the screw in a different location, and a professional can identify your model and show you where to adjust it. If you have no isolation valve upstream of the PRV, a plumber can install one so you can service the PRV without shutting off water to the whole house.
Frequently Asked Questions
How often should I adjust my pressure reducing valve?
You should not need to adjust it more than once or twice a year. If you are adjusting it monthly, the valve is likely failing internally and needs replacement. Seasonal changes in water temperature can cause slight pressure swings, but the valve should hold its setting across weeks and months.
What happens if I set the pressure too high?
Pressure above 80 psi will shorten the life of your water heater, washing machine, and dishwasher. Supply lines may develop pinhole leaks. Toilets and faucets are more likely to drip. If you accidentally set it too high, turn the adjustment screw counterclockwise until the gauge reads 75 psi or lower.
Can I adjust the valve if the water is turned off?
No. The valve adjusts under water pressure. If you turn off the water, the adjustment screw will move, but the valve will not actually change the pressure it delivers. Always turn on an indoor faucet so water is flowing through the PRV while you adjust it.
Is it normal for water to leak from the adjustment screw?
A small drip from around the screw when you first adjust it is normal and usually stops within a few minutes. If water continues to spray or stream from the screw after 10 minutes, the bonnet may be cracked or the screw may not be fully seated. Stop adjusting and call a plumber to inspect the valve.
What if my pressure is already below 50 psi and I have a PRV?
Your PRV may be set too low, or your incoming pressure from the water provider may be naturally low. Call your provider to confirm the pressure at your meter. If it is below 50 psi, you may need to remove or bypass the PRV entirely, or install a pressure booster pump. A plumber can test your incoming pressure and recommend the right solution.