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Thread: Crossed Hot & Cold Water Lines

  1. #1

    Default Crossed Hot & Cold Water Lines

    We had a contractor do a kitchen addition about two years ago. We didn't
    do the finish out until 6 months ago.

    After I put in the sinks and faucets, we discovered that we had no hot water
    in the kitchen or the utility room, which were both affected by the remodel.

    I did some sleuthing and discovered that when we turn on the hot water on the new sinks, we have cold water coming in the hot side on the hot water
    heater and hot water coming in the cold water side of the new hot water
    heater. We have two hot water heaters, on for upstairs and one for down.
    I thought originally they might be hooked in series or parallel but when I
    cut off the upstairs, there is no hot/cold water upstairs.

    I had put in 3 new Moen single lever faucets when I put in the sinks, so I disconnected them and tested the system again and had the same results.
    Also, when we had the new hot water heater put in, the old one would not
    drain because water kept flowing in. (It should have been a clue to me that something was wrong at this point. )

    During the remodel, the plumber went into the lines at two different location
    in the slab. I am sure that he crossed the lines were the old utility room. The
    second point is where the old kitchen sink lines were and all that happened there was they were extended to the new island and the new kitchen sink
    counter and since it was the end of the run, I don't think it would be causing
    the problem.

    My questions are: 1. Is there a high tech way to locate the lines in the slab?

    2. If I am right, is there a way to seal the blocked lines without tearing up the
    slab and the new ceramic floors? I think there is a kitchen cabinet sitting
    on top of where the work was done. (I was at the house on one of the days
    the plumber was working so I know about where it was)

    3. We have trusses between the first and second floor, so I was thinking it
    might be easier to run PEX through the ceiling.. All of the runs would be fairly short.

    Any insight would be very helpful. We live in a small town and we have had a
    less than enthusiastic response to helping us fix this. We've contacted three
    plumbers and only one came out and it doesn't appear that he's interested
    in helping us out.

    Thanks
    Last edited by Terry; 12-27-2008 at 09:34 AM.

  2. #2
    Master Plumber master plumber mark's Avatar
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    Talking original contractor out of business???

    I assume that the original conrtactor is not
    calling you back.....

    why did they make a connection under the slab in
    the first place...

    it sounds like you have done your homework already
    but are you absolutely sure that it is not crossing at those moen faceuts..


  3. #3
    Forum Admin, Expert Plumber Terry's Avatar
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    Default

    If it's only the Moen faucets involved, you can pull the handle and spin the cartridge 180 degrees and that will swap the hot and cold.

    If the dishwasher is included in this too, you may want to find a spot farther back and cross it. Like you say, it may be crossed at the water heater. That might be a simple place to cross it back.

    If your water supply to the water heater is going into the hot outlet, that needs to be changed.
    Last edited by Terry; 12-27-2008 at 03:10 PM.

  4. #4

    Default Crossed Hot and Cold Hot Water Lines

    Thanks for the quick replies.

    Actually, I have a pretty good relationship with the contractor. He just doesn't believe that his plumber is responsible. I disagree, of course. I have
    talked to the previous owners and they say there was never a problem.

    The reason the pipes are in the slab is this is Texas and that's where the pipes go, except, obviously, on pier and beams.

    The hot water only goes in the cold water side of the heater when we turn on the hot water.

    I am sure it is not the single handle Moens because I disconnected the faucets at the shut off valves and tested the water and it's still the same problem. The only thing I didn't check was the two handled Moen fixtures
    in the bathroom (they're original tub and vanity) because I didn't think they
    could be the source of the problem.

    I thought I read somewhere that epoxy could be injected into the lines to block them. I think that would allow part of the existing loop to be used and
    it would minimize the amount of sheetrock I would have to tear out.

    I also guess from the sounds of things, they're isn't a high tech way to pinpoint where I think it's crossed.

    Thanks again

  5. #5

    Default

    Turn off the cold water input into the water heaters after setting the water heater to pilot. If something is crossed, you will still get full water pressure out of the hot water tap of each fixture.

    If crossed then perhaps shutoff all of the hot water shutoffs at each and every fixture and see if the cross is still there. There must be some way to isolate the cross.

  6. #6
    Moderator & Master Plumber hj's Avatar
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    Default water

    You need a plumber to analyze the system and see if it can be corrected by simply crossing supply lines at the faucets and water heater. It probably can be done, if there is no toilet or outside faucets involved.

  7. #7

    Default Crossed Hot & Cold Hot Water Lines

    Unfortunately, there is a toilet involved.

    Getting a plumber involved is necessary but not that easy. Out of the three
    we contacted, only one has come out and he really wasn't helpful. I may
    have to find one out of Houston or Austin.

    Since there were only two places involved in the remodel, I think I know
    where the problem is. As noted, one of the places (and the one where I
    think the cross is) is under a newly installed cabinet with granite counter tops) and a complicated framing system for a desk, so attacking the problem
    from the kitchen is impossible.

    It seems to me that the way the water lines are running under the slab is
    from the hot water heater to the washer dryer connects then to the new
    sink area (Where the problem probably is) and then on to the bathroom and then to the kitchen. Does this make sense as a loop? In spite of the sound
    of it, the distance is actually pretty short.

    The reason I think the problem is where the new sink is, is because every
    thing in the bathroom and kitchen is affected and they would both be
    downstream from the problem area.

    How deep would the pipes be below the surface of the slab by code? It
    seems to me that the easiest fix would be to go upstream of the problem
    area. If the slab has to be breached, it would be easier to do it in the utility
    room, because the existing cabinets could be moved and any work to the
    slab and ceramic tile would be covered up when the cabinets were replaced.

    I'm asking all these questions because I want to have a grasp of the details
    before I'm presented with a solution.

    Also, I gather there is no high tech way to determine the routing of the pipes?

    Thanks for all the replies.

  8. #8
    Moderator & Master Plumber hj's Avatar
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    Default pipes

    We cannot possibly diagnose you problem or solution from here, because there are certain decisions that can only be made AFTER analyzing it on site. They have to decide whether the the pipes can be revised so the existing cross connection can be left in place without creating an even larger problem. How to bypass the cross connection, if that is possible. And how to do it without making any connections under the concrete floor, since these are not allowed, and can cause future problems if they are made.

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