The Caraguard website does not explain it properly to my mind. It is what I would call a modular system.
The 1st bit is an electrically operated stopcock that is fitted closely just after the manual one under the ‘van and is operated by a switch unit fitted inside the ‘van. ( Mine is immediately above the light switches next to my main door ).
There are other modules available and I have the drain valves option which auto open when the switch is turned off and taps are opened.This releases the water pressure in the feed pipes which though this doesn’t totally empty these pipes (as the floe does) what little water might be left cannot create enough pressure to “blow” pipework causing frost damage.
So to leave the ‘van we follow the steps —
1 Switch the stopcock off
2 Open taps (incl. shower)
3 Flush toilet cisterns
4 Put anti freeze in all sink & shower drain plugholes, toilet bowls & cisterns.
Total time spent is normally less than 10 mins and all within the ‘van.
As I said it works for me.Linkback: https://staticforum.co.uk/index.php/topic,791.msg2117.html#msg2117