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Thread: main water presure regulator problem

  1. #1
    DIY Junior Member jack99's Avatar
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    Default main water presure regulator problem

    hi everyone,
    jack99
    i have a cash-acme presure regulator that i thank is not controling my water presure. when turn cold wateron to hot water tank the presure keeps climbing, it has an ajusting screw i dont know which way lowers presure.. need help!!!!

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    If the valve was working, and now isn't, it's usually time to replace it. Some of them have rebuild kits, but it's a pain if that doesn't fix it, your labor, time, and money now is all wasted since you have to replace it anyways. Just so we're on the same sheet, this is a prv for a city/town water system on your main input, and not a pump control, right?

    If your WH's safety valve, the T&P is leaking water, you may also have a bad expansion tank, and that may need to be replaced. When you heat the water, it expands, and needs somewhere to go which is the expansion tank.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3
    In the Trades Gary Swart's Avatar
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    If I follow your story correctly, you need a thermal expansion tank to deal with that rise in pressure. When water is heated, it expands. In homes without a PRV, this expansion is absorbed into the city main and you never notice it. However, PRVs have a check valve to keep this from happening. The result is the pressure rises very rapidly when the water heater kick in. If you have a leaky toilet flush valve, the expansion will be dealt with there, but without being released or absorbed, when the temperature reached 150 psi, the T/P safety valve on the water heater opens as it should to prevent the water heater from becoming a bomb. The thermal expansion tank goes in the incoming water supply line between the PRV and the water heater. This tank takes the expansion, holds it until the heating cycles is over, then releases it into the supply line. You definitely need a pressure gauge, available at any hardware store or plumbing supply for around $15. You are wasting your time just screwing the adjusting screw on the PRV with a gauge. By the way, the comment about the water heater becoming a bomb is not a joke or over stated. There are videos showing just how explosive these can be if the T/P is inoperative.

  4. #4
    Plumber jimbo's Avatar
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    Quote Originally Posted by jack99 View Post
    hi everyone,
    jack99
    i have a cash-acme presure regulator that i thank is not controling my water presure. when turn cold wateron to hot water tank the presure keeps climbing, it has an ajusting screw i dont know which way lowers presure.. need help!!!!
    THe MAXIMUM pressure which a typical working residential regulator will pass is 75 PSI. If your pressure climbs above that, no adjustment is possible...it is broke!!! I gather your pressure rises before you even start heating the water. Is that correct????

  5. #5
    DIYer, not in the trades LLigetfa's Avatar
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    Quote Originally Posted by jack99 View Post
    when turn cold wateron to hot water tank the presure keeps climbing...
    That sounds very much like an expansion problem which is not the job of the PRV but rather an expansion tank to control.

    My guess is the OP is measuring the pressure on the cold line and opening the valve at the HWT is releasing the expansion pressure from the HWT back into the cold line.

  6. #6
    Moderator & Master Plumber hj's Avatar
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    Actually, it is hard to decipher what he is doing or when he is measuring the pressure. Whether it is a bad PRV or expansion tank depends on WHEN the expansion occurs and how quickly. We need a more definitive description of what is happening.
    Licensed residential and commercial plumber

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