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Thread: Hot and cold reversed

  1. #1

    Default Hot and cold reversed

    Can anyone tell me what the symtoms would be if the cold feed line to the water heater were connected to the hot side of the water heater and the hot line serving the fixtures connected to the cold side of the water heater?

  2. #2
    Plumber Cass's Avatar
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    The cold line is the line on the right as you are standing in front of the heater.

    Turn on the hot water at any faucet for 1 min. then feel the pipes coming out of the heater. The one on the left should be hot. If the one on the right is hot it is plumbed backwards

  3. #3
    In the Trades Gary Swart's Avatar
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    I casn't speak for every brand of heater, but the ones I've seen have the intake side labeled COLD and the output side labeled HOT right on top of the tank.

  4. #4

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    Thank you for replying. However, am trying to determine whether or not the plumber who installed the water heater simply mixed up the lines when attaching to the water heater tank.

    In other words, what would happen of you took a perfectly working hot water heater and switched the lines... connect the line that feed the faucets to the the cold label (nomally intended as cold intake) and connect the line coming from outside (well) to the hot label (normally intended for feeding the faucets.

  5. #5
    In the Trades Bob NH's Avatar
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    "However, am trying to determine whether or not the plumber who installed the water heater simply mixed up the lines when attaching to the water heater tank."

    If the lines are reversed now, then the plumber mixed up the lines. The only way to tell is to look at the heater and see which is connected at which label. Are we missing something here?

    The labeled cold water inlet is connected to an internal "dip tube" that extends to the bottom of the tank. The hot water comes out from the top.

    Because cold water is more dense than hot, the water tends to stratify with hotter at the top and colder at the bottom.

    The controls of the heater are set to give the top element priority so that when the water is below the set temperature, that water is heated. The lower control is often set a little lower than the top control.

    If you reverse the flow from the way the heater is designed, then the cold water comes in at the top and hot water is drawn from the bottom. Since the heating priority is at the top, you don't get as much hot water as you should.
    Last edited by Bob NH; 12-06-2006 at 01:21 PM.

  6. #6

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    Bob NH,
    Thank you. I think you understand the situation. This is gas so there is only one heat source (at the bottom). So if this were done (reversing the lines), would the flow reverse without doing anything mechanical to the water heater itself? Please look at my "water heater problem" post that I stated yesterday.

    Again, thanks.

  7. #7
    In the Trades Bob NH's Avatar
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    Quote Originally Posted by mmcgady
    Bob NH,
    Thank you. I think you understand the situation. This is gas so there is only one heat source (at the bottom). So if this were done (reversing the lines), would the flow reverse without doing anything mechanical to the water heater itself? Please look at my "water heater problem" post that I stated yesterday.

    Again, thanks.
    Yes, the flow through the heater would reverse without any other action. I don't know the internal details of a gas heater; whether it has a dip tube or not; and I don't know what the effect would be on performance.

  8. #8
    Retired Defense Industry Engineer jadnashua's Avatar
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    Same effect, you want to run the cold water to the bottom, draw hot water off of the top. If they are reversed, you'll only get a little hot water out of the thing, even though the whole thing started out hot.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  9. #9
    Moderator & Master Plumber hj's Avatar
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    Default heater

    If they were reversed then the cold water would enter the top of the tank and have to push the hot water at the bottom up the dip tube and out into the system. You would get hot water until the incoming cold water settled down and stratified the hot water, at which time you would get cold water. In order for this to happen, however without crisscrossing the pipes between the wall and the heater, the pipes would have to be reversed inside the wall. If this had happened, and the dip tube was changed from the cold inlet to the hot outlet, then there would be no adverse effects from doing this.

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