OK, this thread is as attractive to trolls as any, but for serious discussion- what is the actual mechanism of a pipe cracking/bursting due to the water freezing?
OK, we all know water expands when frozen, and this is the root of it, but beyond that... I'll sketch out what I believe the mechanism is using a series of examples.
make a big "U" out of a copper pipe, like this:
| | | | -----------------------------------
fill that puppy with water. Freeze under the following conditions:
1) leave ends open, start freezing at middle, freeze whole pipe working out towards the ends. predicted outcome- no burst pipe
2) Leave right-hand end open, seal left-hand end. Freeze from left to right predicted outcome- no burst pipe
3) Leave right-hand end open, seal left-hand end. Freeze from right to left predicted outcome- burst pipe
4) leave both ends open. Freeze from ends towards middle. Predicted outcome- burst pipe.
Further prediction: the point where the pipe cracks/bursts will be at a point where there is water in the pipe, not ice.