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Thread: insulating buried supply line

  1. #1

    Default insulating buried supply line

    I have to run 200' of buried cold water supply line from one building to another. The excavator thinks he can get down 2-3' before the ledge gets too hard to break up. yesterday he mentioned "maybe only 6" in places.
    4 ft frostline here. Any good insulation methods that will be somewhat flexible, there's gonna be a lot of twists and turns, up and down, side to side, maybe i'm exaggerating.
    Any good methods out there that are somewhat easy on the budget and will do as well as can be expected? (The backfill will be mounded up as much as possible, which should help a little.)
    Also, has anyone had any experience with these retro-fit heating wires that you run thru the pipe? How easy is the installation?
    thanks, jon f

  2. #2
    DIY Senior Member thassler's Avatar
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    You might want to check around and see if any local construction companies have a rock trencher. I had a similar situation as yours and needed to bury 500 ft of line in 6 inches of soil over bedrock. A local outfit used a rock trencher to dig my trench 3ft deep for $12.00/foot.

  3. #3
    Moderator & Master Plumber hj's Avatar
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    Default pipe

    Insulation slows temperature loss it does not prevent it, and once the surrounding ground is frozen, there would be little you could do to prevent the line from freezing unless the water was in almost constant motion, by leaving a faucet, or other device, open at the end of the run. You need a "RamHoe" to break the rock.

  4. #4

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    sounds like the way to go. The guy whose house it is, is in jamaica, and the backhoe and operator are already contracted to dig for the line. i don't think he'll go for the $12 a foot thing, though i personally know you get what you pay for(most of the time), and do it right the first time. trenching is schedualed for tuesday, so we'll just have to do the best we can, maybe shorten the period of continuous freeze, by doing whatever we do. deep mulching may not hurt later on, in addition to what we can put on the pipe.
    thanks for the replies, i'll have to ask him about keeping the water running, i do that myself a couple of times a year here. jon f

  5. #5

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    -Your heating "wire" could be 1/2" pex taped to the main supply pipe and used to pump warm water through when freeezing temps called for it.

    Would be expensive to operate. Would need to blow it empty with air when not pumping warm water.

    -Run the main through light 4" pvc and center it with spacers; blow it full of urethane foam.

    Better to get the trencher or a hammer and bury it deeper....

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    Master Plumber Redwood's Avatar
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    Sounds like the building inspector should have a look!

  7. #7
    In the Trades Gary Swart's Avatar
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    If you frost line is that deep, you're going to have to bury the pipe deep. While running water would prevent it from freezing, in a very cold climate, that would require mega amounts of water each winter. As already pointed out, insulation does not stop heat transfer, it only slows it so that is not going to really help. If you don't do it right now, this will be an on going problem. Obvious, water never freezes when it is pleasant weather and working on frozen water pipe in subzero temperatures is sure not my idea of fun!

  8. #8

    Default insulating buried supply line

    Thanks for the info, i believe what your saying. we ran 1" pe pipe inside 4" solid drainage pipe. the backhoe got down 2-3 ft. its not backfilled yet.
    The line from the well to the main house is the same depth and its never frozen( its only 40' as opposed to 200'). the guy who put that in, put 1+1/2" pink rigid foam over pipe with 12" wide pieces running vertical, as sides, around pipe(like walls and a roof). The owner raves about how the line has never frozen, so i know what he is going to say. the studio is not a living space, except occasionally for a guest, who would have use of the main house facilities.
    we have the 4" pipe ends filled with foam, have not put in spacers, i think we're over budget to get the whole line filled w/ foam. but we're planning to lay 2' wide rigid foam over pipe once backfill sand is level w/ top of pipe, (maybe do sides 6"), if only because it seemed to do something on original line, and once its backfilled its gameover. that may very well be an exercise in futility...but its the plan now. the general contractor assures me that owner wouldn't spring for rock trenching- he knows the budget.
    The heating wire i was talking about is listed at heatline.com. it can be retrofitted or installed as unit w/pipe for new install. it runs inside pipe, and i think its either 3 or 5 watts per foot.
    The building inspector was up at the site yesterday to look at framing, etc. while backhoe was digging for waterline. i'm told he didn't say a word, maybe because its considered an outbuilding.
    i can only recommend the right way to do something based on experienced input, which i've gotten, thanks to you, the decision's not in my hands though. happy spring jf

  9. #9
    Plumber Cass's Avatar
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    if he doesn't want to do it right ...in writing get him to sign / agree that there is no guarantee on it not freezing and bursting.

  10. #10

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    thats right , he will have that understanding( dont need papers signed in this case)
    i knew it may freeze but may have underestimated the bursting part. i know frozen pipes burst but thought the waterline may be a little tougher than say a small copper pipe. if he has to dig it up again, at least its a straight run about 2' deep. jf

  11. #11
    Sprinkler Guy Wet_Boots's Avatar
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    This sounds like the sort of construction practices that can get a certificate of occupancy revoked.

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