In our old weekender cabin there is a fairly large bore plastic pipe that runs from the well (external, underground) to surface under the basement floor. I haven't opened the insulation to check it, but I expect it at least 2", possibly 3". It is exposed under the floor for about 20' until it comes up into our pressure tank.
The exposed pipe appears to be well insulated with foam, yet since the place is not permanently occupied or heated, really cold weather (single digits or lower) will freeze it. While I drain the water system when leaving, this part of the pipe is the low point, so it never drains completely. So far no damage has been done, but it takes ~24 hours with an oscillating heater under the floor to melt the blockage and get things flowing again.
I am planning to add some heat tape to solve the problem. What I had hoped to do was cut a narrow strip (1" maybe?) out of the foam insulation along the bottom of the pipe, and tape the heat tape/strip to the exposed plastic pipe, probably with a metallic adhesive tape. I would use a thermostatic plug, or a temp sensing tape product so it works only in cold temps.
Wondering a few things:
1 - Is the single strip of heat tape sufficient for keeping the pipe thawed? I figured with heat rising and all that, doing spiral wraps would be wasteful (and require me to remove all the insulation). 2 - Can you combine heat tape and insulation? 3 - I have seen "medium" and "high" temperature heat tapes. Is there a "low" temperature one as well? I just need to keep the pipe at 35F or so. 4 - Anybody got a recommendation for a product that will work on plastic pipes and be effective for this application?Thanks!