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Thread: Use of heat tape

  1. #1

    Default Use of heat tape

    Does anyone know if heat tape can be use for burried plastic pipes to prevent them from freezing?
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  2. #2

    Default Re: Use of heat tape

    Properly burried pipes won't freeze.
    Use of heat tape underground is not a good idea. It's not rated for ground contact, and would be a major pain to fix when necessary (no 'if' about it).
    Plus, it uses valuable power.
    If you have a depth/freezing incompatibility problem, you can run PEX through PVC or ABS with pipe insulation in-between, and/or cover the run with rigid insulation for more protection.
    It is best to simply get the pipe below frost level, which varies depending on the climate where you are. It can be anywhere from a few inches up to 6'.
    Last edited by Cariboocoot; May 4th, 2009 at 13:30 PDT.
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  3. #3
    Join Date
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    Default Re: Use of heat tape

    I would use heat tape on metal pipe, but plastic pipe may be too "insulative" to be useful. I'd think that insulation in the vertical sections at the end of the trench would be enough.
    Since you have to trench to bury, go deep enough to not freeze. Your building code likely demands that anyway.
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  4. #4

    Default Re: Use of heat tape

    Quote Originally Posted by Cariboocoot View Post
    Properly burried pipes won't freeze.
    Use of heat tape underground is not a good idea. It's not rated for ground contact, and would be a major pain to fix when necessary (no 'if' about it).
    Plus, it uses valuable power.
    If you have a depth/freezing incompatibility problem, you can run PEX through PVC or ABS with pipe insulation in-between, and/or cover the run with rigid insulation for more protection.
    It is best to simply get the pipe below frost level, which varies depending on the climate where you are. It can be anywhere from a few inches up to 6'.
    Is there a way I can find the frost level depending on my location? ( MAP, publication )
    Flexmax 80, 8x surette S-530, 10x Solar world SW-175, Xantrex SW plus 5548 inverter, All-Power 6000 watts propane generator with auto start.

  5. #5
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    Default Re: Use of heat tape

    i think a local building inspector or contractor would know that information for your specific area.
    i will also add here that dirt can be somewhat insulative and if you put something like heat tape in it there may be a problem with that much heat building up in that confined space and may literally melt the insulation right off the heat tape and could either ignite (if enough air is present) or cause a shorting of the wires.
    NIEL

  6. #6

    Default Re: Use of heat tape

    We have heat taped wrapped around one section of pipe under the house (where the pipe exits the ground and enters through the floor). Despite all of the R-11 wrapped around the pipe, it still tends to freeze overnight when temps get into single digits. The pipe is about 2 feet in length or so. When it's frozen in the morning, we just plug in the heat tape for 10 minutes and have water flowing again until the next morning. Takes very little power and does not generate so much heat as to be a danger. I wouldn't use the tape underground, but you shouldn't have so much of a problem with pipe that's been buried below the frost line, as other have pointed out.

    Marc

  7. #7
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    Default Re: Use of heat tape

    Quote Originally Posted by lorelec View Post
    Despite all of the R-11 wrapped around the pipe, it still tends to freeze overnight when temps get into single digits. The pipe is about 2 feet in length or so. When it's frozen in the morning, we just plug in the heat tape for 10 minutes
    What kind of magic pipe do you have that does not crack when frozen?

    I guess if each end is "unfrozen" then it does not burst.
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  8. #8

    Default Re: Use of heat tape

    Quote Originally Posted by mike90045 View Post
    What kind of magic pipe do you have that does not crack when frozen?

    I guess if each end is "unfrozen" then it does not burst.
    It's a popular misconception that all pipes burst when frozen. The freeze has to be severe enough to force the water to expand beyond the pipe material's strength limits. Even copper will stand up to some freezing. PEX can expand something like 400 times its size before a rupture occurs. Galvanized is fairly thick-walled and will take quite a lot of abuse before it gives.

    But the best is to keep it from freezing in the first place, as repeated frosts will weaken the walls and make a breach more likely each time.

    lorelec/Marc - if your pipes are freezing despite being wrapped with R-11 you either have a really cold climate or the freeze is "coming in" from somewhere else. Not a good idea to have floor space underneath a dwelling getting down that cold anyhow. Take some time to re-evaluate the whole area - you might find some air leaks that can be plugged up easily and save a lot of hassle!
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    Ohm's Law: Amps = Volts / Ohms
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  9. #9

    Default Re: Use of heat tape

    Mike,

    Oh, we've had pipes break before, too. The one under the house is galvanized, I think, and so I imagine that the ice would expand out the unfrozen ends before the pipe actually burst. We had a PVC pipe in the pumphouse shatter into a million pieces a few years ago. Whoever put that pipe in ran it directly into the concrete floor, and of course the pipe broke off right at the floor, leaving me with almost nothing to glue a new pipe to. Oh, and that winter the water in our storage tank froze, too. It was a bad situation all around.

    Cariboocoot,

    Air leaks? Haha...the whole house is one big air leak (it's been here for 30 years and isn't suited to this climate at all). I've learned the limits of insulation up here, that's for sure. It can't create heat, and eventually whatever heat it contains gets lost. So when the temp is 6degF and the wind is gusting at 40mph (not uncommon in the winter), it takes only a few hours for the water to freeze.
    By the way, do you happen to have a Coot?

    Marc

  10. #10
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    Default Re: Use of heat tape

    I came in late and since I am traveling I didn't read the entire thread but,,,

    PEx tubings will not break even with repeated freezings as long as it freeze more than 6'from a fitting. The nature of the pipe allows this repeated expansion without damage. It is usually not the ice expanding that bursts the pipe,, but rather the hydraulic pressure created between a expanding freeze and a restriction such as a valve. Since the water can't compress it is forced to blow out the pipe. Pretty powerful force.

    More importantly there are several heat tapes that are approved for use on plastic pipe and to be insulated. My water system sits frozen in a lake for several months at a time,,, it is insulated to R-40 with Arctic closed cell foam, and has one strand of heat tape on it. When I return,, I put the genny on for 20 minutes and it is thawed.

    Be carefull however since you must use a tape that is approved for plastic,,, and to be insulated.

    CB hunter: My guess is that you will have trouble getting under the frost line. Heatline also makes a heat tape that goes INSIDE a pipe. If you insulate your pipe with Arctic foam to ~R-10 and bury it so that it wind can't get too it you should be fine. You could also design a system to self drain,,, it is not very hard. My Heat line heat tape use 3 watts per foot at 0c, less as it gets warmer. As others have suggested using heat tape 24/7 is pretty wasteful, but if you insulate it, or run the tape in the pipe you can get the WH down to a manageable few. As I say,, I run my 20 minutes,, and that is only after it has been in the ice for a couple of months,,, frozen solid.

    Try www.heatline.com I know there is a US equivalent.

    Tony

    PS My water line stays thawed as long as I use some water every day,, it is set up to automatically drain between pumpings so it won't refreeze. Detail are in the water pumping threads on this site.
    Last edited by icarus; May 5th, 2009 at 22:57 PDT.
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