With water in the pump it can freeze and break, along with the lines from the tank and any water that is in the lines at a low point. That is the reason all water lines are either filled with an antifreeze or blown out with compressed air. Including adding antifreeze to all P- traps so they do not freeze.
It is done in the same manner in homes and cabins that are not heated in freezing temperatures. Ask anyone that has such a dwelling and any plumber that does winterizing. Its the same procedure.
If your theory is true, why is it we have so many posts every spring about ruptured pipes and p-traps from those that did not properly winterize?"
Example: look at the recent post; " P-trap problem need help".
The previous owner stated that it froze and cracked.
