Some1 wrote:

The water pump is down by the lake, and I've seen a system a long time ago
that self prime's the pump, so that you only flick the switch to get the
water going again.
I realise that I would still have to drain all the water lines when I leave.
Would some one here know about this or other systems, like the inline water
heaters?

A submerged pump with a pressure switch and a small leak in the cabin
might work well. The water under the ice might be 39 F. The leak might
be continuous, or it might happen when a thermostat opens a solenoid
valve as the cabin water temp approaches 35 F.

Nick