This is a very important issue, whether you have a hot water system or not, as overnight is when most of the freezing goes on, when you are not using the system.
Interestingly when in use hot water freezes quicker than cold water (check your science books, it's to do with evaporation).
Insulation and bringing equipment indoors is still the cheapest way of protecting your system. If you use an RO system make sure that you wrap this up well as frost will damage your membranes.
I have to admit that I am quite lazy with this issue as I live in mild Cornwall, and it rarely causes us any problems, although even down here we did freeze up the 1 1/4" delivery hose once last winter (waz a cold'un). When I used to use Omnipoles poles we use to have the aluminium jet manifold freeze up (we keep our poles in a tube on the roof) but since going over to other brushes/poles it never seems to happen.
Alex