A while ago I wrote a post on freezing pee. It was a flippant analysis inspired by the stories boy scouts tell about winter camping.
But I recently got an email from a fellow who was trying to prepare his cabin in the mountains of North Carolina for a cold snap. I’d guessed in post that the freezing point of pee would be in the neighborhood of 21°F. Maybe that’s low enough for keeping things from freezing in North Carolina. It wouldn’t cut the mustard here.
Anyway, he’d apparently filled all the drain traps in the cabin with home made anti-freeze and he was emailing to thank me for the post. I sincerely hope he made out alright.
Most of us in harder-freezing climates don’t worry too much about the drain traps. If they freeze, there’s plenty of room in all but the deepest of traps for freezing water to expand up and down the pipe. It’s the in-bound water pipes that are worrisome. Those pipes are full and under pressure, and unless a tap is open, there is no place for the water to expand into when it freezes. It’s the expanding against the unyielding valve that causes the pipe to burst.
When you can’t drain the pipes, the next best thing is usually to just leave the tap open enough to allow a slow drip. The open valve allows some relief of the pressure if you get any freezing, and the constant slow movement of water through the pipe prevents as much freezing. Think of how the surface of a pond freezes before a moving stream. If you have heat on, you can also leave the cabinets open in places like the kitchen sink to get a little warmer air circulating near potential freeze points near external walls. Dishwasher and washing machine connector hoses tend to be vulnerable spots (especially if they’re near external walls) because the machines don’t open the valves unless they’re on.
None of this is a guarantee against a hard freeze. The best solution for winterizing pipes, if you can, is to drain the pipes and blow them out with compressed air.