Tom,
Depending on which Aqua-Hot system that's in the coach that you are considering, it might have one electric element or two. Ours has two (110 and HI) and it will make the water scalding hot!
We have never winterized as we stay in milder climates. The whole purpose of the Aqua-Hot is to use it when it's cold. The engine will circulate the antifreeze through-out the system so you will have very hot water when you arrive at your destination.
You can use the heating system when you are driving down the road without the diesel running because the engine is heating the antifreeze.
If you are using the Aqua-Hot, it should heat the water bay area also so no worries about freezing the pipes. You will love the Aqua-Hot system.
MM.