I've used methanol before, it will clear a short section of ice. I've used hot water and steam before, both work if you can get a hose thru the pipe but we had a pull string already in there, so when we pushed the hose thru it balled the string up and got stuck. So a welder was used. We're not talking a homeowners welder here. Its an industrial job fired by a 4 cylinder gas motor. Not sure why couplings would arc, I just put it in the ground a month ago and I can assure you the couplings are wrench tight. The conduit isn't being used for AC anyway. All circuits are intrinsically safe as probes and sensors are submerged in heating oil in this case.
