Hey - I have been having issues with frozen pipes this year, as in sure other people are. It is the drain from the roof. Is there any heat tape that I can put inside a cast iron pipe. The pipe is under ground so I can not get the heat tape wrapped around the pipe. I need to be able to get some sort of heat down that pipe to stop it from backing up. The last time it froze it was 10’ past the exterior wall, and 10’ from the main, so the city wants nothing to do with it and says its our problem. Any one know of anything that could help me out?