THE BIG FREEZE QUESTION
I have winterised my boat, drained the calorifier and pipes, left taps open etc, but have realised that the water tank is three-quarters full. Due to family illness I cannot get back to the boat. Should I be worried? FAVOURS, via the CB website
TONY REPLIES... It depends where the plumbing runs and what the pipes are made from. Plastic pipes are far less likely to split if they freeze than copper. If they are low down in the boat, well below the waterline and close to the metal hull, they will be less likely to freeze because the water beneath the ice in the canal is warmer and that warmth will travel through the hull into the boat.
The potential problem with plastic plumbing is if the water freezes it can push the connections apart, so when it thaws you will end up with most of the tank water over the floor. However, as you have left the taps open hopefully this will allow freezing water to expand without causing damage.
Personally I allow the water pump to run (with engine charging) until only air exits from the taps, I then remove the shower mixer in case it freezes inside, and leave it at that. If anything did split/push apart, only the residual water in the pipes would leak out. If I wanted to leave water in the tank then I would make sure there was an air gap above the water to allow for expansion and turn the main valve off, to prevent water in the tank draining via a damaged pipe or union.
If you have an instant gas water heater it’s vital to drain it before leaving the boat because they freeze easily causing expensive damage.
Turn off the main valve when you leave the boat