Extending Shower Supply Lines in the slab

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by hobbzilla, Apr 17, 2009.

  1. hobbzilla

    hobbzilla New Member

    Messages:
    5
    I am remodling my master bath and want to extend my shower into my master closet.

    Code:
    FROM:
    
          OUTSIDE  
    __________________________ 
      |      |   | /    \ ||##|
    G |      |:o |( tub  )||()|
    A |      |___|:\____/ ||  |
    R |     /    T--------T|/ |
    A |      |              __|
    G | mst  |__            /
    E | clst |. |           \
      |      |()|         
      |      |. |_______ / \
      |      |\     .().|
    HW|______|!\________|
    ()|WASHDRY|
      |       |
     /       /
    __|_______|
    
    TO:
    
          OUTSIDE  
    __________________________ 
      | |        | /    \ ||##|
    G | |:     o |( tub  )||()|
    A | |________|:\____/ ||  |
    R |     /    T--------T|/ |
    A |      |              __|
    G | mst  |__            /
    E | clst |. |           \
      |      |()|         
      |      |. |_______ / \
      |      |\     .().|
    HW|______|!\________|
    ()|WASHDRY|
      |       |
     /       /
    __|_______|
    
    In side the closet, I have already removed the drywall to reveal the supply plumbing:
    
        
        shower
         head
         || 
         ||
         ||
        {vlv}
        || ||
        || || 
      __|| ||_
     /__ | |__\
    //  || || \\
    ||  || || ||
    ||  || || ||
    ||  H   C ||
    --------------
    SLAB SLAB SLAB
    
    I can only assume the two outside pipes go back down into the slab to make the runs to the tub. I can also assume that the tub has a similar offshoot on the cold to service the commode.

    Is it possible/feasible/cost effective to break up a small section of the slab to relocate the 2 pipes for the run to the shower into the closet 3-4 feet? Or is it cheaper/easier/better to just run all new lines using the exterior garage wall into the closet? My main reason for thinking it is better to just go backwards was that I was not planning on extending the shower all the way to the exterior garage wall.. so I would have to either go into the slab to cover there or bring it down from the attic.

    Thoughts? Any rough estimates to perform this work if I handle all the demo myself? How deep & wide into the slab would I need to go? Building the shower onto a step-up platform is not an option (personal preference).

    If I do sledge/cut/chisel/scratch out the slab, how worried do I need to be about post-tension cables? How would I even know if I have them?
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,802
    Location:
    New England
    Post-tension slabs are more common in earthquake country than elsewhere, but could show up anywhere. There would normally be some warning labels plastered around in places you'd notice them if you had one, but there's no guarantee. If you have them, it's very dangerous to start cutting up a slab.

    Running water lines in the slab aren't a great idea either. As to drain lines, they usually try to run them underneath the slab, not it it except to come through it where they need to be. While drain lines can leak, a water supply line is probably more problematic. PVC is pretty stable and should last a very long time, but copper can be eaten up by some soils, and fixing a leak beneath the slab is often costly and inconvenient...I'd keep them in the walls.

    While possible to leave your shower drain where it is, it's problematic. Most people find it much better looking if the pan has the same height all the way around the shower. This means that if the drain is offset, to maintain the minimum of 1/4" per foot slope, the longest distance from the drain to the wall determines the amount of drop. Say it's 4' on the long side, that equals an 1" drop. But, to the short side, it may be only 1' (maybe an extreme example, but you should get the idea). That means instead of 1/4" per foot on that short side, it will be 4x steeper since the drain must be 1" in that one foot below because of the long side's slope requirements.

    Once you get the plumbing figured out, check out www.johnbridge.com for help with tiling things and building the shower. Look at www.schluter.com and their Kerdi system...really slick.
  3. hobbzilla

    hobbzilla New Member

    Messages:
    5
    Jim,

    Thanks for the reply. From what I can tell, the supply lines are already in the slab. As noted, they are coming up from the slab to the mixing valve and not from the wall. FYI: as the diagram shows, the only wall that intersects the shower plumbing wall is an exterior wall, so I guess the option was to run through the slab, through the exterior wall, or come down from the attic. Whatever the reason they are already in the slab... most of what I have read online is this is the normal thing to do (at least in this part of the country).

    As for the slope delima, I personally don't think that will be a problem. They even make prefab'd bathtub replacement pans and my scenario has the drain feet and not inches away from the offset side.

    One thing to note, is that the coper that comes up through the slab appears to have been covered in a plastic sleeve or sheath. Perhaps to counter any reaction with copper and the concrete slab...
    Last edited: Apr 18, 2009
  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,802
    Location:
    New England
    It's always a good idea to sleeve copper as it goes through the slab. Another thing I don't like about th epipes in the slab or below it (which is probably where they are, then turn up to go through it) is that it is a huge heat sink, and you'll lose a lot of energy running your hot water through the ground.
  5. kingsotall

    kingsotall Plunger/TurdPuncher

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    just seeing how that works
  6. hobbzilla

    hobbzilla New Member

    Messages:
    5
    Well, I'm back and in the thick of it. They say a picture is worth a thousand words....

    I have been informed by several people, that my idea for keeping the drain where it is based purely on my laziness and would not be the most functional or aestically pleasing for the shower. If that is the case, then since I already have to dig a trench for the drain, if worse comes to worse I will just run the new supply lines to the tub in the drain trench.. Are there any issues with that?

    As you can see, it does appear the manifold simply feeds the tub and nothing else. So, I am hoping to move the shower supply just inside the wall and out of the new entrance to the shower. Originally, I was planing on making the old shower part of the new shower and having it a "drying" off area, but still sloped and tiled, now, I think I have decided to save some money and just make it part of the bathroom and move the curb (the thick black line) to the red-dashed line. That also would be a good place for a single glass door if we decide that the draft is unbearable. The halfwall betwen the shower & tub will become a shelving nook for towels, etc.

    Also, is it a good sign or bad sign that the drain is already about 4" into the concrete and there is still concrete left to break up? I'm afraid I'm over a concrete beam being so close to the exterior wall (1.5-2').

    Can the drain be run "in" the concrete? or does it have to be run in the ground under the slab like the supply lines?

    What should I do here? Thanks in advance!

    P.S. I'm no plumber, but is it just me or does that solder job on the manifold look like a first time DIY'er?

    Attached Files:

    Last edited: May 3, 2009
  7. Terry

    Terry Administrator Staff Member

    Messages:
    14,759
    Location:
    Bothell, Washington
    In plumbing, they let you start with the copper. After about a year, they start teaching you how to run waste and vent.
    They figure that after you have been working your pipes around it, you will have figured out some things on your own, then it's much easier to pound in the final bits they will need.

    Code requires that copper joints be silver soldered if covered by a slab.
    Those joints in the picture are above the slab, so they are allowed to be soldered.

    If you remove the slab to move the drain and the water lines, you will want a plumber that can silver solder the new joints.
    You have to do something with those pipes.
    And you only want to do it once this decade.

    I've seen waste lines and copper embedded in concrete, it's best if they aren't. Concrete in contact with copper will dissolve the metal.
    And waste lines tend to move, so they should be sleeved.
    Sometimes, the plastic layed over before the pour is enough.

    Remember to replace the shower valve with a new pressure balanced, up to code faucet.
  8. hobbzilla

    hobbzilla New Member

    Messages:
    5
    Terry,

    Thanks for the info. I was not planning on silver soldering anything if I can help it, I have read that any sort of joint under the slab is just a problem later down the road.. and silver solder weakens the fittings and the pipe itself.. Therefore, I was hoping to open the slab and simply move that manifold into the wall that will stay. I am assuming the slupply lines to the shower run that way anyway, and if I don't have enough slack in the run to the tub, would just run new lines either around the exterior wall or under the slab as they currently all with the manifold staying above slab (but just moved 1.5' into a wall that is staying. The supply lines to the new shower valve will be in a new wall and not under the slab.

    Does that sound correct?

    What do you sleeve the waste line with?
  9. Terry

    Terry Administrator Staff Member

    Messages:
    14,759
    Location:
    Bothell, Washington
    Most anything really.
    Sometimes you can get a thin foam wrap.
  10. hobbzilla

    hobbzilla New Member

    Messages:
    5
    Terry,

    Any reason that the copper and waste lines couldn't be in some sort of larger PVC used like a conduit? That should protect the copper and the waste line... or am I just totally off base here?
  11. Terry

    Terry Administrator Staff Member

    Messages:
    14,759
    Location:
    Bothell, Washington
    Too much thinking here.
    I like to use closed cell foam pipe insulation for the copper.

    And for the waste, as long as the pipe can move a little, it's okay.
    Heck, it's normally ok anyway.
    We're talking expansion contraction as the pipe heats and cools.
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