Pipe heater tape for plastic pipes

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!
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If you do this, be sure the thermostat on the heat tape is left open to the air temp so it will cycle as needed. ww
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The object is just to keep the water from freezing. The thermostat should be placed next to the pipe. Idealy where the low place is where the water is not draining from. Then the insulation. While not likely, it the thermostat is outside the insulation the heat tape would be on all the time the temperature dropped below the 36 deg (or whatever). This could over heat the plastic pipe.
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On 11/30/2010 11:01 PM, gwandsh wrote:

orange heat tape with a built in thermostat. I placed the tape along the bottom of the water pipe with the built in thermostat against the pipe as per directions. Wrapped the tape and pipe with metal insulated tape and then with plain insulation. The thermostat was designed to start the tape if the water got below 36 degrees. They should still sell that kind of heat tape at Home Depot or Lowes.
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gwandsh wrote:

pipe. Maybe Google can help you.
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developed by one of the leading industrial heat tracing companies.
If it is properly installed, there should be no need for a thermostat, although when I used it many years ago, I did put and ambient unit in the circuit.
The purpose of any kind of pipeline heater is to replace the heat loss through the insulation. __________________ Bill Waller New Eagle, PA
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google PyroWire. no need to strip insulation, but you will have to insert a special elbow fitting before your tank in the heated space.
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