John Walliker wrote:
Self-regulating heating cable under pipe insulation should be OK, with a frost
thermostat to activate it when temperature is just above freezing.

I suppose I could wrap some trace heating cable around the tank, under some
(rockwool) insulation. On a score of 1 to terrible, how bad an idea does
this sound?

(is trace heating cable rated for being exposed to moisture?)

Theo