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OT Plumbing

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  • OT Plumbing

    I have a run of about 60 ft of 3/4 PVC just barely under ground, a few
    inches of landscaping rocks in part of the run. The pipe is drained when
    it even gets close to freeezing so that part is not a problem. Recently
    due to the neighbor having a concrete block wall built quite a bit of it
    became uncovered. I see that it looks like it has become bowed as
    though it expanded in length and because it is constrained at both
    ends, one going vertically against another block wall and the other
    going down into the ground, it sort of buckled. Not to cause damage
    to the pipe but now when I am going to reburry it won't lie in the
    shallow "ditch". The question is with the coeficient of expansion of
    PVC and a year variation of about 100 deg F, is there some sort of
    "device" or layout method to accomodate the length change?????
    Idealy it should not require several large holes that would require
    covers etc.
    Any ideas or past experience???

  • #2
    You could use an PVC expansion joint.
    Home, down in the valley behind the Red Angus
    Bad Decisions Make Good Stories


    • #3
      if its that close to the surface its going to freeze, dig it deeper, at least thats what i did with mine.
      hope it works out, if its deep enough expansion should not present a problem as the temp down there is stable


      • #4
        Don't know the expansion numbers, but plastic expands/contracts quite a bit.

        Above ground a dog leg (2 90* ells w/ a foot or two of pipe between to form an off-set) to allow expansion. Not sure how that works underground?



        • #5
          I haven't done the math on the coefficient of expansion of pvc but I do know off the top of my head that it would be a significant amount for a 100°F temperature variation over 60'.

          The dog legs that uute mentioned would certainly work, if as he stated, they are unconstrained. As long as it is only cosmetically covered with loose clean gravel, it can move.

          Another option to the expansion joint I mentioned earlier is of course a flexible loop in the center of your pipe run. This however would entail a small covered hole to allow the the loop room to move without constraint.

          The ultimate solution is to bury the line to a depth where temperature variation is negligible. I'm sure you are aware of this and want to avoid this if possible, that's an awful lot of digging if you have to do it!
          Home, down in the valley behind the Red Angus
          Bad Decisions Make Good Stories


          • #6
            [quote=Willy]You could use an PVC expansion joint.


            Ah Ha. That is what should do the trick. I've never seen them.
            Now to find somene here in town that handles them.
            Thanks. If not too expensive I'll put two in just to help account for the
            drag due to friction with the covering.


            • #7
              I have re-read this several times and don't see the problem.

              I know that it has been exposed and that it is snaking etc.

              You were happy with it before in it's low tech state with no joints etc. Put it back using your original technique and it should continue to work as before.

              'Problem Buried' = problem gone.