I have on my condensing boiler water outlet pipe inside just below the boiler a diverter that I can divert water into a plastic bucket I cut a piece out of the pipe and replaced over the pipe with a see through pipe that has a red ball in and a knob to turn so when outside pipe freezes up I have the knob turned so water goes down a plastic tube into the bucket. Had it for 4 years and no struggling to defrost outside