Now my strategy is temperature-based: Close the pool when the water temperature falls persistently below 65℉. In 2017, this should've been Veteran's Day weekend.
We took the following steps and are hoping they are sufficient for our situation:
- Keep the water balanced and clean all the way until closing.
- Ideally, while the water is circulating the day before closing, drop in loading doses of Chlor-Brite, Fresh 'N Clear, Algae Control, Ultra Brite, Pool Magic+PHOSfree, and Metal Free from the closing kit that Leslie's Pool Supplies sells.
- Turn off the booster pump, remove the Polaris cleaner and replace its threaded wall port with a plug.
- Backflush and rinse the filter.
- Waste-pump the water until the level falls to the skimmer sill. Monitor the water level very carefully towards the end of this step.
- Grab the "Gizmo" skimmer inlet plug and keep hold of it through the next step.
- Giving the system your full attention, set the pump to "Manual" at the highest RPM. Deliberately waste water until the pump draws air. Run over to the skimmer, screw in the Gizmo, then run back to the pump and turn it off for the season.
- Open the pump stop cocks -- two at the bottom of the main pump and one at the bottom of the booster pump. Put them in the pump strainer and secure the lid.
- Turn the multi-valve to the "Winterize" position and open its bottom drain.
- Detach the inline chlorinator and let the trapped water drain out.
- Still in the pump house, close the just-above-ground first-intake and last-output valves.
- Remove the waste hose from the multi-valve, reel the hose in, and close up the pump house.
- Install the pool cover.
(This is an update to my earlier post, "When to close the pool".)