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Old 05-07-2013, 06:16 PM   #1
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water pressure reducer - how to test?

Bought a new water heater and the pressure valve on the side lets out water every so often. I read that the water pressure reducing valve to the house needs to be adjusted when that occurs. Did that. Turned the valve rightie-tightie all the way. Problem persists. How do you know if the main water pressure reducing valve to the house is working or not? If I turn it right all the way water still goes through. I am not sure how to measure the pressure. How do I know it is adjusting the pressure correctly?


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Old 05-07-2013, 07:04 PM   #2
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The simplest way to measure the pressure is to purchase a low cost pressure gage which typically screws onto a faucet. The gage will give you a direct readout of the pressure at the faucet, which will be a good indication of static house pressure provided there is no water flowing at the time of the reading.

I doubt that overpressure due to a defective pressure reducing valve is causing your problem. Typically the temperture/pressure valve on a hot water heater is set to begin dripping at about 100 psi. It is unlikely, but not impossible, that you are getting 100 psi through your pressure reducing valve, but this is easy to check with a gage.

More likely is that the pressure reducing valve includes a backflow preventer, and you may not have an expansion tank in the house. This topic has been discussed many times on this forum, and it seems to be a common problem, specifically a lack of an expansion tank becomes a problem when a pressure reducing valve or backflow preventer is installed on city water. You will see this kind of problem as the water heats up in the tank. The water wants to expand, but there is no where for it to expand, so the pipes pressurize, and eventually reach 100 psi, which is the point at which the relief valve goes off on your hot water tank.

The solution is usually to install an expansion tank. Exactly where to install the tank would be worth discussing with your plumbing inspector, once you determine if this is in fact the problem.


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Old 05-07-2013, 07:33 PM   #3
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I agree with Daniel.... but I did have an instance of a brand new waterheater leaking its TP valve, tested the water pressure which was at 90PSI, adjusted the PRV down to 60-70 and solved the issue.

Google pressure reducing valves, I could swear they work in reverse of what you'd think, and try cranking them the other direction. I could be wrong... bad memory. (Might save 300 or so, 50 plus install depending...)

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Old 05-08-2013, 12:04 AM   #4
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MTN REMODEL LLC is right on. Turn nut counter clock wise to lower pressure through the PRV, clockwise to increase.

Since it comes preset from the factory from 50-60 psi you'll need to get it back there. Do you remember how many full turns you made so you can get it back to the factory setting? Otherwise do as Daniel suggested and attach a gauge to the nearest available faucet.
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