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Thread: pipes in outer wall

  1. #1

    Default pipes in outer wall

    im thinking of rerouting pipes from an inside wall (no contact with exterior wall) to an exterior wall to my shower. is there a problem with that? i live in nj where it can well below freezing in winter.

  2. #2
    DIY Senior Member finnegan's Avatar
    Join Date
    Aug 2005


    Running water supply pipes in exterior walls is permitted, but discouraged for the reason you cite. The likelihood of a pipe freezing is increased in an outside wall. But, if you have to do it, then go for it. Minimize the amount of pipe in the exterior wall and do you best to insulate the wall cavity and the pipe. Armaflex pipe insulation should work well.

  3. #3
    DIY Senior Member plumguy's Avatar
    Join Date
    Jul 2005


    Installing water lines in outside walls here is not permitted unless there is no other possible way of installing and permission is given by the local inspector. A lot of times a fake wall or such would have to be installed with proper insulation and the pipes being right on the face of the interior wall. I've repaired many frozen pipes and it is not fun cutting into new walls,floors and ceilings because of improper installations. So, if you can avoid it do so!!

  4. #4
    Forum Admin, Expert Plumber Terry's Avatar
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    Aug 2004
    Bothell, Washington
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    Some areas allow for pipes in the outside wall, the Seattle area being one of them.

    From my experience with Winter repairs, I would say "NO" to pipe insulation in the wall.
    I would keep the pipes to the warm side of the wall and insulate behind the pipes. I would not let any insulation get between the pipe and the warm side of the wall.
    In severe cold snaps, it may be a good idea to open up cabinet doors to allow warm air flow to the wall.

  5. #5
    DIY Senior Member Cal's Avatar
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    May 2005
    Northern Virginia


    Any way you can put them in a 6" wall? Can you build a 2" wall on the face of the 2x4 wall you have now ? That will give you a FULL 4" of insulation behind them.

  6. #6


    Necroposting, sorry, but this was exactly my question too. It's about 10 degrees here today and I'm thinking about exactly this issue. I'm putting a 60" tub and shower into the end of a room where the studs of the walls are exactly 60.25" apart, so it's a tight squeeze. It's a short room, too, so what I've done is put the doorway off center at one end of the room. As you walk in, the small vanity is on your right in the corner--turn right 90 degrees and you're facing the sink and mirror. Right in front of you is the toilet, backed up to the left wall. Beyond that is the tub. It should actually flow pretty well, but everything is close. I've been modeling it with boxes and rolls of insulation standing in for the fixtures, and it's not uncomfortable to get around. But the right end of the tub will have easy access, while the left side of the tub will be only about six inches away from the toilet tank. So my wife wants a right-hand tub, reasoning that we want the controls and faucet on the right side, where we can step in at the "front" of the tub and where she can reach the controls when she's kneeling next to the tub to bathe the baby.

    I'm fine with that, but that would be the only place in the house where water lines are going to run through an outside wall. The roofline outside ends near the 2nd floor, so all the pipes above floor level will be in an outside wall. The wall on the left would be an interior wall . . . .

    So what's the best way to insulate that outer wall? It can get well below zero Fahrenheit here in the winter. The house is ancient and drafty, but I've taken these walls down to bare studs and sealed every gap, crack and nail with expanding foam. There won't be any air moving between the studs where the pipes are located.

    So, questions:

    1. It sounds like I want the pipes right up against the backerboard, but won't the control valves determine the depth of the pipes in the wall?

    2. What is the best insulation between the pipes and the outer wall sheathing? Spun fiberglass (the pink stuff?) or should I be filling the remaining space with more of the expanding foam? It's a very small space, so I'm not concerned about cost.


  7. #7
    Retired Defense Industry Engineer jadnashua's Avatar
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    Sep 2004
    New England


    On a normal tub/shower valve, yes, the valve would determine the depth in the wall. There are alternatives, if you like the style. I had access problems and chose a surface mount valve. The entire valve is on the surface...just the drop-ear and supply lines in the wall. This is a Grohe valve. I think they may have some other styles. The outlet at the bottom is for a handheld shower hose...the valve has a built-in divertor. it comes as a shower-only valve as well. The thing weighs probably about 12# - the entire main body is solid brass.
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    Last edited by jadnashua; 01-25-2009 at 01:35 PM.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014


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