I have an 'indoor' pool. It is 4000 gallons. It is an exercise pool that will have a 'fast lane' installed in it. We intend to use it year round.
The skimmer sticks out the side of the pool, here's a pic. I don't think this has much of a freeze potential.
There is also the normal PVC plumbing, maybe 25 feet of it exposed, going to and from the pump/filter/heater.
I have read the manuals for several pool control systems, and they all seem to have a 'freeze mode' where they simply run the pump and then alternate between spa and pool supply/returns. i will be doing a similar control in my PLC-controlled version.
I am considering adding heat-tape as a backup plan, mainly in case we lose power and I need to protect the system using my small generator. In this case I can wrap the pipe easily enough, what have folks done with the filter and pump?