I have a tentative plan. I was inspired by
this thread, where a member from Canada managed to run his pool through Jan and eventually year round. His pool is far larger than ours, but located in a similar climate.
In our case, our pool is much, much smaller. The dig sheet says it's approx. 7,000 gallons, but I believe it's closer to 6,000. It's a kidney shaped in-ground fiberglass pool that runs 3 1/2 - 5 feet deep. You can liken it to a very large hot tub. Currently, when we run the heater and pump at 2000 RPM, we gain 2-3 degree per hour without a cover.
Our equipment pad is outside, near our house. I plan to construct a temporary enclosure around the pad, to keep snow off of the equipment while still maintaining proper ventilation for the heater. I'm still thinking through the best way to construct this, so any thoughts are welcome!
I'm imaging a greenhouse type enclosure constructed of plastic/wood and staked to the ground. Perhaps with a solid plastic top over the pump and filter and side/top ventilation over the heater. My hope is that the enclosure around the equipment will be heated by the operation of the pump/heater a bit, which will help with any snow that falls.
It seems the consensus is that the water temp should be maintained just above 70F, to prevent corroding the heater. So, my plan is to try and maintain that temperature throughout the week and bump it up to 90-95 whenever we plan to use it.
I'll also reprogram the pump for "winter hours", so that it runs at high speed for just enough time to allow the heater to kick on and maintain that 70F temp, then drop to a much lower RPM to just keep the water moving. In the thread referenced, above, it appears that not circulating the water will help maintain heat. However, I fear on cold nights that pipes and equipment might freeze if it's not circulating and the heater isn't on. The slow circulation is insurance against freezing lines while minimizing heat loss. Perhaps I will experiment with running the pump/heater in short bursts throughout the day/night, so that the water never stops flowing for more than an hour or two, while still maintaining heat. Last thing I want to do is destroy my new pool/equipment in our first year of operation!
We had a 2500 gallon koi pond with a large waterfall that we kept running all year. The pond had large koi and the previous owners had always operated it this way. The water wasn't heated. The pump ran continuously and while there was a lot of surface ice, the pump and plumbing never froze. The line was only a few inches below the surface of the ground where the majority of our pool lines are much deeper. I'm hoping the combination of the heated water and circulation means we won't freeze.
Of course, the pool will be covered with at least a solar cover. I'm looking into insulated covers as another option as well. They make them for commercial pools (think ski resorts).
Our pool has a SWG, I'm debating whether I should remove it in the fall and use liquid chlorine or keep it operating since the water temp will always be above 50F.
Final thought on all of this - right now I plan to keep the pool operating through the holidays, close it and re-open in the spring. Typically, the brutal cold doesn't hit until Jan/Feb. Depending on cost and how it all works out (do we actually use it), we will either abort and close early or keep it running all winter. I plan to estimate the cost per hour to run the heater in the next few weeks which will hopefully give me a good idea of how this will impact our gas bill. Since the pump is VS and uses only a few hundred watts at lower speeds, I'm not overly concerned about electricity. Plus, we're used to running a larger koi pond pump 24/7/365, anyway, which was a lot more expensive.
Then the question is, when we "close" do we just stop heating the water and keep it circulating so we aren't looking at an ugly winter cover? Or, do we drain, blow the lines and cover for the 3-4 month "off season"? I guess that's a topic for another discussion.