A good friend of mine who is normally a practical person, had heard the weather forecast on more than one occasion, saying it was going to get very cold etc etc. He had emptied the water tank but didnt let the water out of the taps, shower or loo !. Anyway he went into check the van saturday and inside the van was -4 ! he put the heater on left it a day, switched on the pump to see what he may find but the pump wouldnt work, he left it another day and checked this mornig and all is well, it all works fine, that was very lucky me thinks.