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water lines in slab

radmix Member Posts: 194
I have a large ranch house that it would be easier to run the domestic water lines in the slab before it is pored than drilling holes later. My question is should I insulate the water lines. If I don't the cold water line may become warm form the slab during the heating season but I am afraid that the 1/2" wall foam may crack the slab later because of the give of the insulation.



  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    water lines in slab

    In my house, the water lines are in the slab. I have no idea if they are insulated or not, but the cold water gets noticeably warm during the heating season, especially if it is cold out (outdoor reset runs the slab warmer as it gets colder outside).
  • Paul Pollets
    Paul Pollets Member Posts: 3,593

    Water lines should be placed UNDER the slab, not in the slab. The piping should be sleeved and protected as it comes through the slab. Insulate the lines with 1/2" or 3/4" wall neoprene. as required.
  • radmix
    radmix Member Posts: 194
    water lines in slab

    This house is all concrete. The second floor will be steel decking with concrete on top and the domestic lines will have to go in the slab. I'm just wondering is the insulation (armor-flex) will be a problem with the integrity of the concrete floor.

  • Mark Eatherton
    Mark Eatherton Member Posts: 5,840
    Thats a question for a structural engineer...

    Having done buildings like this, we ran the heating and water distribution mains in Unistrut below the metal decking and placed penetration sleeves in the slab wherever and whenever we needed to. Who would want to look at ugly corrugated metal ceilings in the building space?

    Don't forget, if you have radiant floors in that slab, you'd best insulate the back side of the slab, or suffer the consequences...

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • radmix
    radmix Member Posts: 194
    water lines

    This house consists of a 1st floor garage then the 1st floor of the house both slab on grade but are 25" form each other then the second floor which is the steel decking which will span each so there is a 25" breeze way in between which they want to be exposed underneath. The  water lines will have to go into the slab to go from the garage to the first floor.

  • Charlie from wmass
    Charlie from wmass Member Posts: 4,250
    Are you in a warm climate?

    Being a New Englander we could not make that run due to the months of September through May when it gets below freezing.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
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