Pressure Reducing Valve issues

Old 05-17-11, 01:14 PM
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Pressure Reducing Valve issues

Hi all,

When I replaced the leaking hot water heater at my mom's house this weekend, I noticed that she has water pressure of 110psi. YIKES. I was measuring this at the hose bibs on both sides of the house (one of which is the first branch past the pressure reducing valve that's located where the main water supply enters the crawlspace). I tried adjusting the pressure reducing valve - a Watts Regulators 25AUB - and it did not do a thing to change the pressure.

In case you're curious, I did install an expansion tank per instructions on the cold side of the hot water heater. I only cranked it up to 95psi at installation b/c I wasn't feeling good about having it be so high.

I came back the next day to address the pressure and here's exactly what I did:
1. I put a pressure guage - a new one, same brand as the one I used the day before - on the spigot closest to the pressure reducing valve and tried adjusting the pressure at the pressure reducing valve. I had googled the instruction manual for the valve and it told me to turn the adjuster counter-clockwise to descrease water pressure. No change.
2. I had my mom go to the other spigot, open it for 3 seconds, close it, and come back to the guage read out the pressure. It would build back up slowly from 40 to 60 over the period of about 1 minute, and then at 60psi it would climb rapidly to 110psi in about 30 seconds.
3. I haven't dealt with a failed pressure reducing valve before, but I must say I was nervous about turning it much further counter-clockwise because I thought I might end up unscrewing the adjuster off of the valve body (laugh if you must).

My questions:

A) can I turn the adjuster counter-clockwise as far as possible without fearing it will come off of the valve body (and create a huge gushing leak)?

B) Do these valves go bad? This one might be 28 years in service (house built in '83). They look so sturdy and industrial that I just don't think about them failing like that but that's why I'm here asking.

C) Is there something about measuring pressure at hose spigots that it throwing this whole thing off?



Last edited by Chrisatunc; 05-17-11 at 01:19 PM. Reason: clarification
Old 05-17-11, 02:13 PM
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Yes they go bad. Replace it. The range of these is only 25 to 75psi. If you going over 75 psi its NG regardless how far you turn the nut.

Hose bib measuring is fine.

Mike NJ
Old 05-17-11, 07:55 PM
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Years ago outside hose bibbs were sometimes connected before pressure reducing valves (PRVs) to give maximum pressure to garden hoses. This is no longer allowed where I live. I think that connecting a test gauge to the drain on a water heater or to a laundry connection is easier.

It would build back up slowly from 40 to 60 over the period of about 1 minute, and then at 60psi it would climb rapidly to 110psi in about 30 seconds.
This tells me that the air cushion in the expansion tank is set at 60 psi. The air cushion needs to be set at the same pressure as services the water heater. If you set the pressure of the new PRV to 60 you should be fine.

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