[Smurf]

You know when it's really cold as can end up with the water in the van tank  frozen solid too.
In prolonged sub zero temps when you can't work for day's/weeks in bad winter months cheapest form of frost protection is to just drain everything down properly including the van tank/s and bring kit indoors.

There is no point in trying to beat mother nature.

Are you in Scotland, Smurf?

I think only once has it come close to that in SE Wales.

One bad winter down south I was was laid up for at total of 6 weeks post op, Anyway the weather was so bad I could have not worked anyway even if I wanted, During that time the water in the van tank turned into one big block of ice as that was the only thing I had left in the unheated van which I forgot to drain down.