Make sure you system is completely empty every night when it freezes push water through hoses with a home made valve to go on van tyre, that will use a bit of the air to push all the water out, ideally use a spare wheel or 12v air compressor. If its empty it cant freeze set pump up on quick release so you can take it inside. Run a piece of tumble dryer duckting from heater blower to back of van let van run half hot in morning will heat back if van up just a few ideas that worked for me