wa8yxm wrote:
Finally, The reason freezing damages pipes is because they are FULL of water which expands when it solidifies (turns to ice) in this it is unique, only substance on earth that does that. However if the pipe is say half full of air,, no damage can be done, since air, unlike ice, compresses very easily (ice too can be compressed but it is not done easily) (This last is proven by ice core samples at the polar ice cap by the way, the bottom is denser than the top, indicating compression).
Close, but not quite right on the theory - the ice expands and compresses the air, and it is the extreme air pressure that cracks the pipes. That's why they are always split some point after the ice, and why the plumber's advice to always leave a tap open in extreme weather. Of course, if your system allows two plugs of ice to form, then the piping in between is at risk!
I agree that if you hear gurgling, then the water is not out of the system. Even with my large tank compressor, I have to do the pressurize, rest, repeat thing several times before I stop getting anything out of the faucets.
