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HW Heater Pressure Relief Valve Leaking

David_16 Member Posts: 50
We just had a sprinkler system installed yesterday and I just noticed that the HW heater pressure relief valve is dripping hot water occasionally.

I had the boiler tech just come out and he said that I need to have an expansion tank installed on the HW heater and that he's certain that's the issue. He was unable to do it on the spot and suggested I find out why the sprinkler guys didn't do it.

Does that make sense?

Also, we are leaving on vacation tomorrow morning. I turned off the boiler and shut off the water to the boiler. But, I still want to run the sprinklers because we have a newly seeded lawn that will need water.

Will I be safe for the week that way? It's going to be 45-70 degrees out while we are gone.


  • Jamie Hall
    Jamie Hall Member Posts: 22,117
    It should be safe. I'll bet the sprinkler folks installed a check valve or backflow preventer... which, of course, should be between the domestic water and the sprinklers, but if it's on the main coming in then yes, you do need an expansion tank.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • David_16
    David_16 Member Posts: 50
    edited April 2016
    Yes, I'm pretty sure they installed a check valve/backflow at the main down in the pit at the sidewalk. I think that's typically where the town requires it to be installed. I'm sure I could be wrong about that.

    I have an appointment with my boiler people to come out and install an expansion tank when I return.

    Very worried about leaving for a week though. I really want to keep the water main on since I have new plants that need to be watered or will die.

    The dispatch manager (not a tech) said with the boiler power off, if I run hot water and use it up, the boiler wont call for new cold water and should be close to empty so it's not like it could leak too much even if it did leak or if it really blew the valve, it's not going to continuously leak, does that make sense?

    How safe am I leaving the boiler power off, water to the boiler off (but the hw heater doesn't have any valve to turn off cold water into the hw heater) and letting the sprinklers run? I shouldn't worry?
  • Leon82
    Leon82 Member Posts: 684
    Follow the pipe back there may be a valve downstream a little bit.

    I've had some sediment block a prv from sealing also.
  • hot_rod
    hot_rod Member Posts: 20,740
    You could turn off the water to the house, or turn the water heater to vacation mode
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Jamie Hall
    Jamie Hall Member Posts: 22,117
    So long as power to the boiler and water heater is turned off, you should be fine leaving the water on. What is happening is that when cold water is heated is has expands, and with that nice new check valve in place, it has nowhere to go -- so the PRV pops. Just turn off the power to the boiler and the water heater.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • David_16
    David_16 Member Posts: 50
    No problem while I was away.

    Came back and turned on boiler again and later that evening had a funny mothball type smell in house. Called FD and they detected some low levels of CO and thought that the burner was putting out some CO when that kicked in. Does turning the boiler off for a week have anything to do with that?

    Boiler tech installed the expansion tank. Confident that will remedy the problem with the overflow water dripping out. Now he's giving the boiler/burner a thorough cleaning.

    He also tested the water pressure and said we are at around 85-87 or so and we should look into a plumber installing a pressure reducing valve. Is that something that would be recommended?