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Thread: Unexpected water lines in shower remodel

  1. #1

    Default Unexpected water lines in shower remodel

    The guys over at John Bridge forums sent me over here to see if you all have any suggestions. Im in the middle of a master bath remodel and after tearing everything out have found a bit of an issue with the water lines. House is SOG, copper water lines. The new shower will include the old shower plus a hall closet. The old water lines ran in the wall between the closet and shower. Initial plan was to cap off the water lines and run new through the attic.

    After taking out the wall between the closet and shower we found a cold water manifold, a concrete patch around the manifold (under the hardwood in the pic), and some mysterious stubbed up, not-crimped-off water lines in another wall (visible in the wall on the other side of the hardwood).

    To orient you a bit, when you stand facing the water lines (as in the picture) you are facing the front of the house. The main water line comes in on this side of the house, from the front. The manifold where the water heater interfaces with the water lines and they fan out to all parts of the house would be about 12 behind you- more or less in line.

    Breaking out a small area of the patch revealed the water lines in question to be, from left to right: - hot water. Manifold- the left line appears to be the main line coming in from the front of the house and veering up to come out of the slab (and continue on to shower & tub as a line). Have not chipped out the concrete enough to see this directly, but are within a couple inches. Middle line runs toward the HWH manifold. Right veers off to the right a bit and back- think it probably goes to the toilet supply line.

    The mystery lines are cut under the slab in this area and were identified via air from an air compressor, they do not appear to be attached to anything.

    Bottom line, I need to do something with this manifold so that it isnt sticking up in the middle of the shower. Getting water from it for the tub & shower is not necessary, I can run new lines to service them.

    Other info that may be pertinent: copper line runs from street to a shutoff valve a foot or so in front of the house. From the valve box outside to this shower manifold is about 15. Another 12-14 from the manifold in the shower to the main manifold. That is, assuming everything runs in a semi-straight line.

    Thanks in advance for any suggestions!
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  2. #2
    Forum Admin, Expert Plumber Terry's Avatar
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    Aug 2004
    Bothell, Washington
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    I don't know if you removed the caps from the mystery pipes or not, that would be the best way to determine where they are from.
    It's hard to say, why they are there.
    If you want to move the manifold, you may also need to break out more concrete and relocate in another spot.

  3. #3


    Thanks, Terry.

    The mystery pipes have no caps, crimps, etc they are open on top and cut off under the slab. Other than curiosity as to how it was all originally plumbed they are probably irrelevant.

    Can the manifold be relocated? I was advised that a joint/splice under the slab is unwise. The main water line comes from one direction and the other 2 lines go off in the other. I'm not sure how this could be relocated without a joint. I really would prefer not to break out large areas of concrete, but I do need to do something about the current situation.

    See if this picture, taken a little further back helps any. The tub was to be relocated in front of the current door to the shower, you would then enter the shower where the tub is currently. I would be willing to relocate the manifold into any (read: least invasive) wall and just run the water lines for the tub & shower to the shared wall btwn the tub & shower.

    In the pic the main water line comes into the manifold from the left, the other 2 lines then go off to the right.

    Thanks again!
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  4. #4
    Moderator & Master Plumber hj's Avatar
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    Aug 2004
    Cave Creek, Arizona

    Default water

    1. Joints under the concrete floor are not wise and are discouraged.
    2. If #1 is not possible, (and in your situation that is most likely, unless the floor can be broken and the lines turned up in a different wall, and then new continuous lines run to the new location), the lines have to be silver soldered/brazed, not soft soldered.

  5. #5


    I have had a plumber come out and look at the situation. His recommendation is to silver solder joints and move the manifold over to another wall. He says they do it all the time in slab leak repairs and that the silver soldered joint will actually be stronger than the copper line itself. So, my questions here are:

    1) Do you agree with that statement, are the joints actually stronger than the copper line?
    2) Does the silver solder deteriorate over time (or does something else occur) that would cause a leak?

    IF the solder doesnt break down over time and IF the silver soldered joint IS stronger than the regular line it would seem there would be no inherent risk of a leak from the joint- at least no more so than the currently existing risk of developing a leak. He also mentioned covering the area with some type of a rubber casing/boot- but I don't recall if that was just where the manifold would otherwise be in contact with the concrete, or if it was over the joint too.

    Option 2 would be to rebuild the manifold closer to the slab, in a swale chipped out of the slab (in order to get it lower) and run the lines for the new shower and tub just on top of the slab. This avoids any under slab joints, but would necessitate some creative work on the shower floor. The plumber says he can rebuild the manifold lower- and is actually doing this in a remodel currently (though I dont know that its in a shower). From a plumbing perspective what do you think about this option, would it be preferred to the under slab joints?

    We are fairly certain the main line comes into the manifold, then goes back down and continues on to the main HWH manifold. The 3rd line in the manifold looks to go to the toilet. However, this is based on logic, the floor plan, and the direction the pipes run. If, by chance, this is not the main line we possibly could just terminate the lines at the manifold and run new water to the area. Is there any way, short of cutting open the pipes/ manifolds or breaking out large areas of slab that I could determine definitively where these lines run? More specifically, if the line coming in is the main line or not? Ive attached a floor plan of this side of the house (this is the new floor plan, not the current one) showing were all the water lines are, hopefully it will help. The laundry was the first part of this remodel and all its water runs above slab. The sink backing up to the laundry is new and will get its water above slab, too. There currently is a second sink over by the other sink in the master bath- it has water lines coming up through the slab that are not notated on the diagram. There are no other manifolds in the master bath, nor behind the bath toilet. I have not accessed the bath sink to know if there is a manifold there. I have not found a manifold at the exterior faucet, but have only taken the sheet rock out on one of the walls in that corner. I suppose there could be one on the other wall. The water lines for the other part of the house are a good 30 to the right of this side of the house.

    Any thoughts?
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  6. #6


    We have determined definitively that the main line comes into this manifold in the shower and then on to the main manifold. I have two options to remove the manifold from what will be the middle of the new shower:

    1) Silver solder the main line together under the slab thereby eliminating the manifold (this would be the only underslab joint, all other lines- tub, shower, toilet- will be ran in new from the attic.)

    2) Rebuild the manifold closer to the slab and raise the shower floor slightly with screeds.

    My concern is an underslab leak. I'd welcome any comments as to which method would be preferred, as well as any comments on my previous questions on silver solder.

    Thanks in advance.


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