Water – Do I need to replace this water pressure valve

If you are on a municipal system and have pressure that high, you quite likely already have a pressure reducing valve (PRV) installed near your water meter. The International Plumbing Code requires PRVs on any water supply over 80psi. If this is the case, your PRV may just need adjustment. As they age, the spring regulating the device's operation can soften. Or it could be faulty and need repair or replacement. If you do not have one, you need to have one installed.

If you are on your own well with a pressure tank, the pressure switch controlling pump off operation needs adjustment. Other types of systems should have similar arrangements to control pressure.

How to adjust a PRV. There is typically a bell shaped housing with an adjustment screw and lock nut on top. Loosen the lock nut and turn the adjuster counter clockwise a small amount. The adjustment can be rather sensitive. Operate the faucets and toilets in your house to allow the system to equalize to the new pressure setting. Take a new pressure reading. How much it changed will give you an idea how much more adjustment is needed. Typical water system pressures should be somewhere in the 40-60 psi range. Shoot for the high 50's.

If the PRV controls supply to a fire sprinkler system (it normally shouldn't), you will need to check with a fire supression professional to determine if and how much you can reduce the supply pressure.

If you do need a new PRV, check with your municipality, they sometimes offer rebates to help mitigate some of the cost.

At 140 psi, either that valve is shot, or you need to install/check your expansion tank. To know for sure, after running some water for a second, stop any running water and check your pressure again. If the high pressure only occurs after the hot water tank has been heating back up, then what you really need an expansion tank.

To replace this valve, after turning off the water, unscrew the union fitting on the bottom of the PRV (at least I'm hoping that's a union, it should be two pieces and the nut should move independently from the pipe). You should be able to work on that with a crescent wrench one partial turn at a time. Then with that disconnected, you should have some play in the pipes to pull it slightly out from the wall and unscrew the valve from the top threaded connection. Installing the new valve will be a similar procedure in reverse, just clean off the threads and apply some pipe dope to the male threads first.