Cheap winter drain down

Don't know if this has already been done?

1. Get a tyre valve from any tyre place. They cost £1.30, but I was just given it as I had my tyers done there.

2. Use an old water inlet pipe, put the end in hot water and push the tyre valve on.

3. Check with the caravan water system makers if it is OK to pressarise the system to whatever PSI. Mine said up to 15psi was OK.

4. Connect digital pump for correct pressure and away you go.  COST £nil