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Underground Insulated Pipe

Brian_18 Member Posts: 94


  • Brian_18
    Brian_18 Member Posts: 94
    Underground Insulated Pipe

    I'm installing underground insulated pipe(s) to bring heated water from my coal boiler, to my house. I've received widely different advice from as to proper installation. One theory suggests installing to a depth of 36". Another says 24" over the top is fine. The frost line in my area (sometimes) reaches 12" during a harsh winter. I could bury to 36", but my soil conditions are clay & shale. I know I can easily run into ground water at that depth. Logic would say it's better to keep the pipe dry, and a little higher than to bury deep and have water in contact. Any recommendations?
  • Brad White
    Brad White Member Posts: 2,398
    The idea of depth

    is based on frost line depth. If within the frost zone (above frost line, naturally), ground heaving can distort your piping -or worse.

    A happy medium would be below frost line but above your water table. The use of sleepers may be a good idea (concrete railroad ties are nice if you can get them) to spread out the weight if the soil below frost line is unstable.

    As far as water intrusion, depending on what conduit system you are using (Perma-Pipe with an HDPE outer jacket is hard to beat), your system should aim to be water-tight anyway.

    If your frost depth is only a foot, man, you do not need that much heat anyway :)
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"

    -Ernie White, my Dad
  • Brian_18
    Brian_18 Member Posts: 94
    Here's what I'm using

    FYI, this is the insulated pipe I'm using:
  • Brian_18
    Brian_18 Member Posts: 94
    Here's what I'm using

    FYI, this is the insulated pipe I'm using:
  • Steve Ebels_3
    Steve Ebels_3 Member Posts: 1,291

    I agree with Brad's advice.

    (don't tell him that, it'll go to his head)

    If you haven't purchased your tubing yet you may want to investigate this method. We've had excellent results using bare tube and hiring a foam insulating company to cover the tubing for us. They fill the bottom of the trench to about 4 inches, we lay the tube in place and then they foam another 4-5" over the top. Where the tube passes under a drive, we'll place an additional 2" of rigid foam board on top of the tube/foam combo already in place. Works great and is usually a bunch cheaper than preinsulated tubing, especially in the larger bore tube sizes. We're doing 650' of 2" next week and I'll see if I can take some pics of the process.
  • Weezbo
    Weezbo Member Posts: 6,232
    A Ditch Witch

    or some one handy with a pick Maddox and shovel . insulation is something we are Keenly aware of here. depth is good...insulation like foam is good...within some abs . we used pre insulated Abs piping then have the foamers arrive and blast a bit more on the pipe and fittings for G.P.'s suspending the foam pipe off the ground over some Poly sheathing until it is foamed... then, if you would like to add DHW or control wiring,from a distant point no problem...sealing the ends inside a building doesn't hurt for safety reasons.
    you can run multiple lines in 3/4 size or 0ne inch,1 1/4" haven't jammed any of the 1 1/2 or 2 " through insulated ABS yet though ...however i do know that the tubing is Not the same diameter in Insulpex and the 1 1/2" O barrier product...the wall thickness is thinner in the Insulpex.outer wall is like the old silly little millimeter commercials of the 60's ...
  • Brian_18
    Brian_18 Member Posts: 94
    Thanks & sorry for double post

    Thanks for the advice, I already have the insulated pipe, and plan to install this week while the weather is still good. My main concern is ground water. I know from past experience digging on my property that I run into shale at 48" usually with ground water. The insulated pipe that I have is inside 5" corrigated drainage pipe. I plan to pull another pvc sleeve over it as a second barrier to water just in case. I dug a short section of the trench last night to 36", and I'll wait until I get home this evening to see if water seeps in. I will also shoot the grade and see if I can put in a french drain to my property line (ditch), and maybe provide drainage at 36" depth. I think I will loose heat more rapidly if the insulated pipe is sitting in water, rather than higher up in dry(er) ground. More foam in place is not in my budget. It's funny how all the technical brochures for insulated piping systems show installers in nice sandy soil, NOT in muddy clay that sucks your boots off when you try to walk.
  • hot_rod
    hot_rod Member Posts: 22,103
    You're correct water will..

    really wick away the heat. That pre foamed tube in a corrugated sleeve should be water proof. But you still don't want the whole assembly in water or worse near running water.

    This you need to address with a drainage system or a sump pump pit. Adding insulation would not help the water table issue. It's an installation issue not a product issue, really.

    My issue with that pre-insulated product is the thin R-value where the tube inside is closest to the outer wall. i doubt you will ever see more than 1" in that location.

    I prefer the Insulseal to that pre-insulated tube. It has a true R value all the way around. it glues together for a water tight seal, and allows you to remove the tube if necessary.

    Here are the two products side by side.


    hot rod
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Brian_18
    Brian_18 Member Posts: 94
    Always comes down to $$$

    HR it comes down to economic payback. The twin tube product I'm using is actually the same company that makes Insulseal. (Flexsulseal) I was able to buy an end of run length of their old design product, which has full length foam around the tubes instead of their new "dead airspace" design. The size I have is made with 1" Kitec PAP and inserted in 5" poly drainage pipe. Most are built around 4" pipe, the 5" ID gives a little more room for their shaped foam. I'll know tonight if I can put in a french drain to keep everything dry, and if not I'll only bury it at 24" deep. As my grandfather said, "It's a great life, if you don't weaken" Over the years I've come to know what he meant.
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