(206) 949-5683, Top Rated Plumber, Seattle
Results 1 to 6 of 6

Thread: Hot Water Heater - hot water expanding back into cold pipes

  1. #1

    Default Hot Water Heater - hot water expanding back into cold pipes

    When I run cold water at any faucet, the water gets hot after a few seconds, then gets cold again. I checked for crossed/touching pipes, and heating/defrost devices. None found.

    So I figure that as the hot water heats in the hot water heater tank, it expands, sending hot water back up into the cold water intake line.

    I understand that I can put a valve (bleeder or balloon, etc.) inline in the cold water intake line to prevent this backflow.

    Is that correct?

    If so, what is the valve called? Can you show an online example of availability? Are there any installation/operational concerns?

    Or is there a different solution?

    Thanks,

    -Dan

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    Location
    New England
    Posts
    21,428

    Default

    They're called heat traps. They come in pairs, one for input one for output - they are also color coded to help you figure out which is which. They've got a sphere that floats or falls in the appropriate direction to seal the convection path, but opens when you turn on a faucet. One downside, because the hot water is more effectively held in the tank, it may take longer to get it when you want.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3

    Default

    Interesting, but not what I was mentioning. How do these traps prevent/address pressure from building up in the tank? If hot water doesn't have anywhere to go, (no open faucets, can't go back into the cold send) pressure can get more than silly.

    That's not to say that I know where the hot water would go with one of these (balloon or bleeder or whatever) valves I'm talking about installed.

    Ideas?

  4. #4
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    Location
    New England
    Posts
    21,428

    Default

    I think that you'll find that it is convection...water does expand when it is heated, but not enough to push it up to the cold water faucet - if it did that, it would more likely push back out to the street rather than up to a closed end (otherwise the pipe or washer, or something would split, to relieve the pressure). Water doesn't compress - something has to give as it expands.

    People run into problems if they have a pressure reduction valve (which acts as a one-way valve) sometimes. In that instance, an expansion tank is usually recommended/required to prevent blowing out a seal or pipe.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  5. #5
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Location
    Cave Creek, Arizona
    Posts
    25,659

    Default heat

    If your analysis is correct, and that is not a given, then a check valve on the incoming water supply to the water heater, in conjunction with an expansion tank to minimize pressure build up, will cure it. But first I would do some checking to be sure that is actually the problem. It would normally only apply if the water heater was in a basement, and then you could feel the main cold water supply by the water heater to see if it was actually getting hot.

  6. #6

    Default

    Right on. I'll confirm and reply back. Thanks

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •