Here's how I do it: I raise my FC up to shock level, then add 1 full quart of Polyquat (I have 20k gal). I then wait 48 hours for the FC to drop, and then add more chlorine to get it back to the shock level, then close.
Closing for me means waiting for the water to drop to 60 degrees, then dropping the water level below all the returns and the skimmer, then plugging them. I then plug the low drain. Since I have an AG and the plumbing is exposed and on quick-releases, I remove it all, drain it, and store it in the basement.
But I have my solar panels that form the deck. I blow them out, removing key bridging hoses so that each section (each side and each end of the pool) can be blown out. This takes hours as the connections all can trap water, which is my biggest fear. Filling them with anti freeze would be SUCH a waste of time and effort that it would be easier to disconnect each bridge, but I'd rather not do that either.
If I start opening in mid-April and get the pool open by the beginning of May, I never have a spring algae problem. If I have to wait and don't get it open until late May (as I did this season) I had a small algae problem that was cleared up in 24 hours by hammering it with liquid chlorine, technically "too much" as it could have bleached the liner, but my liner is old and ugly anyway!
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