Lukewarm water from series heaters

Discussion in 'Water Heater Forum, Tanks' started by Emanon, Sep 25, 2016.

  1. Emanon

    Emanon New Member

    Joined:
    Sep 25, 2016
    Location:
    Nebraska
    The problem: our water is lukewarm, at best.

    We moved into this 1990's house a month ago. The second water heater (both electric) plumbed in a series was non-operational. We had it replaced. Each heater works individually when isolated, but if we try to run both at the same time we have lukewarm water. I tried turning up the temperature - the first is at 135 degrees and the second at 140 - with only marginal improvement. Both have electricity to them. The exit pipes are hot to the touch on both. Any ideas what the problem might be?

    I've attached a picture of the set up. Water comes in from the right and exits up on the left.

    Thank you for your insight. image1.JPG
     
  2. dj2

    dj2 In the Trades

    Joined:
    Aug 13, 2013
    Location:
    California
    From the picture, it looks like the "cold" from the right feeds into the hot coming out from the water heaters.

    The proper installation would be: cold goes into the water heater "cold" side only, and not mix with "hot".

    BTW, shut off valves on the hot pipes as they come up are not necessary.
     
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  4. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    Something is wrong with the second water heater, although I cannot explain how you get that symptom. The WH has two thermostats and two heating elements under the two hump on the side. If the top thermostat senses the temperature needs to rise, the top element turns on. If that is warm enough, the bottom thermostat gets a chance to receive power if its thermostat calls for heat.

    Now is this a problem with the setting on one of the thermostats on the second heater? Or is it some other problem. I don't know.
     
  5. Emanon

    Emanon New Member

    Joined:
    Sep 25, 2016
    Location:
    Nebraska
    dj2 and Reach4- Thank you for your responses.

    I discovered the problem, or at least a temporary solution. See the pipe coming from the bottom of the water heater on the right (the first in the series)? I closed it and immediately we had hot water. I was told that this pipe was designed to supply hot water to the hot water faucets farthest from the water heater exit on the left, so those faucets wouldn't have to wait long for hot water. With both water heaters functioning, I noticed that this pipe was cold. I shut it off and immediately we had hot hot water.

    The odd thing is when using the first water heater in isolation with this pipe from the bottom open, this problem doesn't exist. Its only when using both that we have lukewarm water. Can anyone answer why?
     
  6. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    Yes, a recirculation system is intended to keep the water in the pipes hot so that when you turn on the hot in the bathroom, the water gets hot quickly. Usually there is a pump and a check valve (one way valve) to move water from the far end back to the cold input. I don't see how that pipe can be cold and still explain the symptoms, unless the check valve failed, or you don't have one.

    Now there are systems where there is no check valve. Explaining the symptom of not working with both WHs powered, but working when either is powered... nothing comes to mind right now.
     
  7. rjbphd

    rjbphd In the Trades

    Joined:
    Mar 6, 2016
    Location:
    Chicago, Illinois
     
  8. rjbphd

    rjbphd In the Trades

    Joined:
    Mar 6, 2016
    Location:
    Chicago, Illinois
    Check valve or pump is NOT needed if the system is piped correctly. .
     
  9. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    Can you think of an explanation of the symptoms in the original post?
     
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