I've had in-ground vinyl pools for over 20 years, been a member of PoolForum for many years, & just joined this forum.
Like a lot of people, I have this phobia (paranoia?) about pool closing, freezing pipes, algae, etc. So I've been reviewing the pool closing instructions on this forum & comparing them to the ones on PoolForum.
There is a small coflict regarding the Polyquat. The instructions on this forum doesn't include Steps 5 & 6 from the following link: http://www.poolforum.com/pf2/showthread.php?t=8084, that I've excerpted below. Apparently Polyquat causes the FC to go down. Is this a concern? Thanks!!!
[2) Let the water get cold. I turn off the solar panels and remove the solar cover (which is either cleaned, dried and stored, or trashed). I want the water to be AT LEAST in the low 60's when I close--50's is better.
3) I run the Free Chlorine level up the shock level appropriate for my Stabilizer/CYA level. Since CYA is around 40ppm, Shock Level is 15ppm.
4) I add a quart of Polyquat 60% algaecide to the return stream and let it act for 48 hours.
5) I then check my FC level, which usually has dropped like a stone (from the Polyquat) to very low levels--even zero. Don't panic, it's normal.
6) I add bleach/Liquid Chlorine to bring FC back to Shock Level (again, this year it's 15ppm). Now I'm ready to physically close the pool."