I know this is a bit late after the big freeze has gone.
But I thought I would share what I do so as to not have any cold related problems.
My van is on the street so can't have electric to it.
So I use a car tyre inflator to purge all the water out of my system and by using a gate valve I am able to clear the tube from my tank. As I use hozelock connections, I remove my pump to the house to keep warm.
I had an old tyre pump and put on a male hose tail coupling. (Picture)
By using a nylon reducing connector I am able to join a Series 21 Female hose coupling to the hose with the aqua stop connector. I just connected to my system and clear out all the water.
When clearing the pipe to the tank, once I turn on my pump. I close the valve mid way and this allows the air to stay in the tube instead of water.
It works for me.
And I suppose, that's about it.