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Thread: Hot water recirculation loop

  1. #1
    DIY Junior Member tb's Avatar
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    Nov 2013
    San Diego

    Default Hot water recirculation loop


    I have a 3/4" loop sticking out of my drywall in the garage next to the water heater. A neighbor that has lived in the devolpment since they were new tells me that it is a loop to install a recirculation pump.

    I originally thought this was for a water softner, but a few years back I installed a softner and used this loop....oops, uh nope. I wish I could remember the details, I think when I had the feed shut off to the softner I was still able to get water out of faucets. That was when I asked the neighbor and he said it was a recirculation loop.

    This is a southern California house built in 1980

    Is there any way I can confirm (without pulling down drywall) this is loop for a pump?
    If it is a loop do I need a check valve?
    Is there a standard for flow direction when these where installed, if not am i assuming correctly that once the system is drained and the loop opened that I can open the main valve a bit, fill my system, and figure out flow direction?

    thanks in advance

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  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    Sep 2004
    New England


    The pictures don't help me...maybe a plumber.

    If the house was plumbed for a recirculation loop, at least one fixture would have a T on the hot pipe so that the hot water could get back to the WH.

    Where is the WH in relation to those pipes in the picture?

    The simplest loop would be one that uses gravity. You do need a check valve to prevent water from the bottom of the WH (where it is likely cold after some use) to be pulled out of the hot line at the point of use (i.e., two parallel paths...some will try to flow both ways).

    To keep the energy costs down, when there's a pump involved, you typically need something to slow or stop the recirculation once the end point of use gets hot. On some systems, they turn off the pump, on others, there's a valve that closes.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3
    Forum Admin, Expert Plumber Terry's Avatar
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    Aug 2004
    Bothell, Washington
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    Your best bet would be to ask the neighbors if they have used the recirc line, and ask to see how it was done.
    A picture of piping at the water heater may give a clue too.

  4. #4
    DIY Junior Member tb's Avatar
    Join Date
    Nov 2013
    San Diego


    nothing unsual on the water heater, the other pipe you caan see is going to a garage sink.
    I don't know what to think now about the neighbors....a different neighbor says it's a waster softner loop, funny thing is he has a water softner, but it's not hooked into that loop?? I may take off the loop, cap off the two 3/4" pipes and see if I can get any clue from that procedure.
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  5. #5
    Plumber Sean Beck's Avatar
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    Jun 2013
    Toronto, Ontario, Canada


    I would cut into the 3/4" copper pipe and add a 'tee' and a hose bib. Open to hose bib to see if it is in fact a hot water line. If it is, then isolate the cold water supply to the HW tank and open the hose bib once again. If the there is no pressure, then you will know the piping is connected to that HW tank and is more than likely a re-circ line.

  6. #6
    Moderator & Master Plumber hj's Avatar
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    Aug 2004
    Cave Creek, Arizona


    "recirculation loops" do NOT have a "loop' like that. It SHOULD be a softener loop, since that is the only reason they usually install a pipe like that. I would have to know what happened when you used it for a softener. The only way to tell what it is would be to cut it apart and then start testing flows to see what makes it work.
    Licensed residential and commercial plumber

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