Pressure relief valve (California)

Discussion in 'Plumbing Code Questions' started by Danhome, Mar 13, 2017.

  1. Danhome

    Danhome New Member

    Joined:
    Mar 13, 2017
    Location:
    California
    so I'm in Los Angeles, Ca.

    My house has galvanized main pipe to a pressure regulator and a small relief valve into the house.

    Had a plumber redo the main line w copper and a new regulator. However he didn't add a new relief valve. He said I have one near my tankless water heater and doesn't need another one. My street pressure comes in at 180psi. How do I find the code to see if a relief valve is needed up front or if just one near the tankless is sufficient. Thank you!!
     
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Joined:
    Sep 2, 2004
    Occupation:
    Retired Systems engineer for defense industry.
    Location:
    New England
    I'd be surprised if CA allowed a relieve valve...they essentially can become a major leak and waste of water.

    With a tankless WH, most places would not require an expansion tank, but with a conventional tank, you would unless you wanted the relief valve to be opening each time the WH ran, but that's from thermal expansion, not supply pressure.

    The PRV can fail, and note, some of them have a limitation in the amount they can step the pressure down...if your water pressure is high enough, some would require you do add a second one to step it down in stages to keep it within design specs. All a relief valve would provide is a way to limit the maximum pressure if the PRV fails. The one he took out may have been set to something like 90-100psi. The plumber's right in a way, in that you probably do have a relief valve on the WH, but most of them are set to 150psi, which is much higher than you want in your home. If the PRV did fail, instead of the relief valve you had opening, the one at your (probably much higher pressure) tankless would open. So, you have to decide if there's a failure on your PRV, with your 180psi supply, where do you want it leaking, and how high do you want the pressure to get before that happens?

    FWIW, most people do not utilize a relief valve when they install a PRV (pressure reduction valve). My guess is that most people would notice the pressure rising and replace their PRV before the pressure got all the way to your supply, and probably prior to the relief valve opening. I suppose if it were a catastrophic failure, a relief valve might be useful as long as it was plumbed so that water release wouldn't cause damage, because if it got to that point, 180psi water could make quite a stream of water! But, PRV's do not typically catastrophically fail...they fail gradually.
     
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  4. Danhome

    Danhome New Member

    Joined:
    Mar 13, 2017
    Location:
    California
    Wow thank you for that!!!! I think ok with just having a relief valve at the WH
     
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