[quickthrowman]

It’s easy to control a valve actuator based on a space temperature sensor reading, monitor the space temp and when it hits setpoint, send a signal to the valve actuator to open up. Add in a flowmeter on your drain pipe and you can even close the valve when the water is done draining. Probably there is a fitting with a valve and flowmeter in one.

The difficult part is opening up all of the plumbing fixtures and taps automatically, I haven’t tried draining water out of a home’s plumbing system without opening all of the taps and am unsure if it works.

If you have a well, you’ll need to drain the expansion tank and turn off the water pump, the latter can be achieved with a relay that breaks power to the pump but I’m unsure of how to handle the former.

You’ll also need to automate filling the traps with antifreeze, unless you’re cool with replacing sink traps and toilets after a freeze event.