Heat trace on plumbing vent pipe

[cce]

Hello,

I live in northern Alaska and sometimes during extreme cold spells the vent pipe for the plumbing in homes will free shut. Usually all the needs to be done is to crawl up on the roof and dump boiling water back down the vent to thaw it out. I have a owner that has just built a large cathedral style home with steep pitched roofs. He wants to be able to heat trace the vent so he will not have to try and crawl up on the roof if it freezes shut. Does anybody have any ideas? Could you drill a hole in the vent pipe inside the attic and insert an capillary tube type heat probe up the pipe? EPD Breaker of course, but does anybody have any other ideas or solutions? You would need to have heat trace in both the attic portion and also the portion that is above the roof line I would think.
Thanks for the help

[ron]

I'm not a plumber, but I believe that the water level in a vent pipe goes nowhere near the roof line level. If you can experiment with the water level in that pipe, then only heat trace from there down. Probably the circumfrencial type of wire wrap would be better, rather than penetrating the pipe.

[Len_B]

I would try electric heat trace (self limiting type)on the outside surface of the vent pipe, and then cover with pipe insulation in the attic and outside area. Ref NEC Art 427

http://www.nelsonheaters.com/Product...les/Cables.htm

Len

[cce]

It is not water that makes the pipe freeze. Its frost build up inside the pipe. Also, If I were to heat trace I would have to wrap around the pipe inside the attic and then try to transition through the roof next to the pipe to wrap around the portion that is on the outside that sticks above the roof. That transition where it goes through the roof is what has me puzzled. Also, in this instance the pipe actually is not in an attic at all. It goes up through the roof in a 6 inch wall. So There would never be any access to it.

[tom baker]

I moved this to the NEC topic. Tom