Polyquat and closing

Polyquat will use up some chlorine, but not huge amounts. If you are concerned with keeping FC as high as possible you need to allow 24 hours after the polyquat addition, then test the FC level and raise it up to where you want it. Doing this helps a little, but is only going to make a small difference overall (compared to adding polyquat and raising to shock level and close the pool without waiting.)
 
So, let me see if I understand. Assuming good pool chemistry, no algae or CC, and wanting to have FC last as long as possible over a long winter; the plan is:

Raise FC to shock level, add polyquat, wait 24 hours, redose to shock level. Close.
 
Sure.

However, that isn't what I recommend doing. What you described doing is better at preventing algae than what I recommend, but not enough better to be worth the extra effort (in my opinion). I shock a day or two in advance, then add polyquat right before closing (just enough time before closing to mix it into the water), and don't bother with bringing it back up to shock level a second time. The chlorine won't last all that long regardless. They key thing is to make sure there isn't any live algae (even minute/invisible quantities) when you close. Having a high FC level is part of that, but but being right at shock level at the moment you close isn't essential.
 
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