Typically the way this works is its a closed loop with antifreeze in it for cold weather and it coils through a water cylinder to do the heating. So the water t

Typically the way this works is its a closed loop with antifreeze in it for cold weather and it coils through a water cylinder to do the heating. So the water that flows through the roof panels never goes anywhere. There are a few reasons for this, mainly the extremes of weather both hot and cold you don't want 90C water in your shower nor to freeze water in the system and break it. All of which adds to the cost any complexity but if you dont do it they don't work.