Loosen the lock nut, then turn the adjusting bolt clockwise to raise pressure or counterclockwise to lower it. Watts says the LF25AUB-Z3 ships preset to 50 psi, and any time you adjust the valve you must check the result with a pressure gauge. Never bottom out the adjusting screw on the spring cage.
What does Watts say about adjusting the valve?
Watts gives the whole procedure in a few lines. The regulator is factory preset to 50 psi (344 kPa) in a static condition, meaning with no water running. To adjust the pressure setting, you loosen the lock nut and turn the adjusting bolt. Clockwise increases pressure. Counterclockwise decreases it.
Two rules go with that. First, any time a reducing valve is adjusted, use a pressure gauge to verify the pressure setting. Second, do not bottom out the adjusting screw on the spring cage. In Watts's parts drawing, the adjusting screw is item 53, the lock nut is item 51 and the spring cage is item 3.
Before using a two-indicator instrument for adjustment, identify the retained red hand versus the live reading on the cited Watts gauges. A maximum saved from an earlier period is different evidence from the current static setting.
### How do you adjust it step by step?
The sheet gives the actions but not a numbered list. Here they are in order, with the gauge steps drawn from the sheet's rule and from EPA guidance:
- 1Attach a pressure gauge. EPA's WaterSense sheet says to attach the gauge to a hose bibb, the cold-water faucet for the washing machine hookup, or a cold-water faucet on the first floor, and to turn the water to the fully open position.
- 2Read the static pressure with no water running. Watts's preset is stated for a static condition, so that is the reading to compare.
- 3Loosen the lock nut on the adjusting bolt.
- 4Turn the bolt a small amount. Clockwise raises the pressure, counterclockwise lowers it.
- 5Read the gauge again before you turn further. Repeat steps 4 and 5 until the reading is where you want it.
- 6Tighten the lock nut and read the gauge one more time.
Steps 3 and 6 follow from the lock nut's purpose. Watts says to loosen it before adjusting, and the sheet does not describe retightening, so tightening it afterward is our reading of how a lock nut works. Follow your own valve's instructions if they differ.
### What should you write down before you change anything?
Note the static reading, which hose bibb or faucet you used, and the time of day. Read the model off the valve's nameplate too. Watts says to specify the model shown on the nameplate when you order parts. With those notes, you can put the setting back if the change makes things worse, and a plumber can see what you started from.
### Why should you check the pressure more than once?
Street pressure is not fixed. The City of Phoenix says water demand during peak times and during times of little demand is one factor that may result in a slight variation of water pressure. A single reading right after you turn the bolt tells you where the valve sits at that moment. A second reading at a different time of day tells you whether the setting is steady.
Watts sells a tool for the longer view. Its troubleshooting section names a pressure test gauge, model 276H300, that registers the highest pressure reading over the period of time it is left attached to a hose bibb. If you suspect pressure spikes overnight, a gauge like that shows the peak, not just the moment you looked. Our page on whether water pressure suddenly got too high covers the causes of spikes.
What pressure should you aim for?
Watts gives a 50 psi factory setting, rather than a design target for every house. Distinguish that setting and EPA's recommendation from the plumbing code's maximum.
| Source | What it says |
|---|---|
| EPA WaterSense | Recommends incoming service pressure between 45 and 60 psi, and says most U.S. plumbing codes require pressure regulating valves where supplied pressure exceeds 80 psi |
| IPC Section 604.8 | Requires a PRV where pressure within a building exceeds 80 psi static, reducing building distribution pressure to no more than 80 psi static |
| Phoenix Design Standards Manual | Requires a private regulator on the customer's side of the meter where local static pressure exceeds 80 psi |
| Watts | Ships the LF25AUB-Z3 at 50 psi static |
Phoenix's customer service guidance includes 120 psi wording as well as an 80 psi regulator requirement. That conflicting utility-page wording does not make 120 psi an acceptable setting for building distribution piping. Follow the 80 psi static limit in IPC Section 604.8 and the city's design standards, and use EPA's 45 to 60 psi recommendation as a starting target where it meets the home's needs. Private regulators on the customer's side of the meter are the owner's responsibility. Our page on whether you need a pressure reducing valve explains the distinction.
EPA's sheet explains why the lower range matters. It says high water pressure can damage plumbing piping, fixtures and appliances, and can lead to increased water consumption, premature equipment failure and risk of leaks. Our page on what home water pressure should be covers the range in more depth.
### Is 50 psi the right setting for your house?
For most homes, the factory setting already falls inside EPA's 45 to 60 psi range, so many owners never need to touch the bolt. If your gauge reads outside that range at the fixtures, adjusting is worth considering. If the reading is far off and the valve does not respond to adjustment, the valve may be worn. Our page on signs your pressure regulator is going bad lists what to look for.
What are the risks of adjusting it yourself?
The first risk is a wrong reading. A gauge on a hose bibb shows the pressure at that point and time. EPA says to verify the pressure from each supply if a home has more than one, such as an independent source for irrigation. The second risk is bottoming out the screw, which Watts warns against directly. The third is what an adjustment can hide. If the pressure on the house side keeps climbing after you set the valve, the cause may not be the setting at all. Our page on why pressure rises after a Watts pressure reducing valve explains thermal expansion, creep and debris.
Watts also says the valve should be installed by a licensed contractor in accordance with local codes and ordinances. That sentence is about installation, not adjustment, but it is a fair signal that the maker expects a professional to be involved with this valve. Our page on how to install a Watts pressure reducing valve covers that side.
When should you call a plumber?
Call if the gauge reads above 80 psi with no water running, if the pressure will not hold the setting after you adjust it, if the bolt is at its limit and the pressure still will not come down, or if you see water at the valve body. HQ Plumbing & Air is licensed and insured, gives free estimates, quotes an upfront price, and offers 24/7 service. For a wider look at whether you need a valve at all, see do you need a pressure reducing valve.