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  1. #1
    Join Date
    Mar 2007
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    Western Montana
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    Default Reverse plumbing to water heater

    Two electric 52-gal water heaters plumbed in series (cold water supply to one, then out to 2nd WH, then out to hot supply for house).

    What puzzled me was that the incoming cold water supply was attached to the 'Hot" connection (on both water heaters), and the feeder line to the house was attached to the "Cold" labeled connection (IN) on the water heater. Ok, so sloppy installation, illiterate plumber or whatever. However, what got me wondering more was the fact the hot water temperature at the kitchen sink only measured at 105 degrees at hottest, despite the fact that the thermostat control settings on both water heaters was set to Hot (normal hot at top heating element), and Very Hot (at the bottom element). I do not carry an amp meter to verify current at the heating elements (though now I think maybe I should start).

    My Question - Doesn't the 'Cold' connection feed through a dip tube to the bottom of a water heater for initial heating? Therefore, by my rudimentary understanding, by reversing the plumbing connections, 'hot' water for the house is being pulled from the bottom of the tanks (eg. hot water rises to the top of the tank, right?). Would reverse plumbing of the supply lines cause a low temperature reading?

    Just to complicate the picture, water heater manufacture dates are 1993 & 1994, and this home is a log home in the mountains that was de-winterized a few days ago (but water heaters should have been in operation for at least 3 days).

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  2. #2
    Join Date
    Mar 2007
    Location
    Dallas, Texas
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    4,112

    Default Re: Reverse plumbing to water heater

    If I understand what I read, you are correct. If plumbed in series, the cold from street/supply should connect to the cold inlet on first heater. The Hot/discharge line out from the first heater then is connected to the cold/inlet of the second heater. The second heater Hot/discharge then is connected to the hot water distribution lines in the house.
    If taking water out through the inlet, then you draw out the coldest water while the hottest water remains at the top of the tank (heated water rises)
    One quick test I do is to simply feel the cold and hot lines after drawing down a little hot water, just to verify the correct connection and thus correct location of the stop valve on the cold water inlet.
    Jim

    Jim Luttrall
    www.MrInspector.net
    Dallas, Texas

  3. #3
    Tim Moreira's Avatar
    Tim Moreira Guest

    Default Re: Reverse plumbing to water heater

    I think he was getting the heated water from the first water heater and it was drawing off the bottom of the second water heater. That's why the temp was warm but not cold.

    IMHO


  4. #4
    Join Date
    Mar 2007
    Location
    Western Montana
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    Default Re: Reverse plumbing to water heater

    Both water heaters are reverse plumbed the same way; in other words, the house cold water supply connects to the "Hot" connection on the 1st tank in the series. Then the pipe runs from the "Cold" connection on the 1st tank to the "Hot" connection on the second tank. The final feeder supply emits from the "Cold" connection on the second tank, and feeds off to the house. At least that's how I traced it, and the final "out" line from the 2nd water heater attaches to a pipe in the overhead floor joists that is labeled "Hot". If nothing else, he was consistent.

    I can't see any damage that it would cause, but as Jim said, it would tend to pull cooler water off the bottom of the tank. I have to go back up there on Wednesday, so will try feeling the water lines (I have tried that in the past, but the physical connection to the tank usually makes the pipes hot anyway). The tanks are also tucked into a small closet making it hard to navigate around.

    Also, what I didn't mention was this home is in a remote mountain area that is famous for amature builders doing odd things so nothing up there surprises me. Oh, and the property only cost 1.6 mil; the house is so-so, but it goes with 90 acres that border the Forest Service. At least the land is pretty. Elk and moose all over the place if you like that sort of thing.


  5. #5
    Join Date
    Mar 2007
    Location
    Ormond Beach, Florida
    Posts
    25,304

    Default Re: Reverse plumbing to water heater

    Not only is it plumbed wrong (as others have said), but you do not have any hot water either (as you implied).

    There is a specific definition which must be met before water can be considered as being 'hot water'.

    From the IRC.

    HOT WATER.
    Water at a temperature greater than or equal to 110F (43C).

    And, every dwelling unit is required to have an adequate supply of hot water.



    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  6. #6
    Join Date
    Mar 2007
    Location
    Dallas, Texas
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    4,112

    Default Re: Reverse plumbing to water heater

    Terry, that sounds like I would be making an excuse to go back just for the scenery. If you run the water while or immediatly before feeling of the lines or hitting it with your laser therm. you will find the flow pattern in actuallity, not just how it is labled. When cold water flows in, the cold line will cool rapidly.
    Good Luck,
    Jim

    Jim Luttrall
    www.MrInspector.net
    Dallas, Texas

  7. #7
    Join Date
    Mar 2007
    Location
    Lake Barrington, IL
    Posts
    1,363

    Default Re: Reverse plumbing to water heater

    Terry, The dip tubes could have been changed from the cold side to the hot side. I don't know of a way to confirm that without pulling things apart. I also agree that checking the wires at the elements with an amp meter is the better way for checking for proper operation.

    Eric Barker, ACI
    Lake Barrington, IL

  8. #8
    dick whitfield's Avatar
    dick whitfield Guest

    Default Re: Reverse plumbing to water heater

    Try running about about a 1/2 gallon of water into a bucket from the drain on the first heater and check the temp of the water.

    Then run about 5 gallons of water from a hot water faucet in the house. Then draw another 1/2 gallon on water from drain at the bottom of the first tank and check the temp of the water again.

    If the water temp is close to the same at both readings then the heaters are most likely hooked up backwards or the dip tube is damaged. If the second reading is a lot lower than the first then the first heater is most likely conected properly. This is assuming that both elements in the first heater are working properly.

    To test the second heater the same way, the water in the first heater would need to be cold.

    Hope this helps!


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