Conflicting Polyquat Pool Closing Info

Oct 14, 2007
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:, 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."

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
San Rafael, CA USA
The subtle difference is that the Buckman instructions say to wait after the shock level of chlorine before adding the PolyQuat. The combination of high chlorine and high PolyQuat has the chlorine break down the PolyQuat into smaller pieces, thereby consuming chlorine. So yes, one could check the chlorine level after adding the PolyQuat (say, the next day) and if too low, raise it up, but it probably doesn't have to be to shock level.

No one has the perfect answer here. It is very unlikely for any amount of chlorine on closing to make it through the winter. The PolyQuat can last longer, but will also tend to filter out (as it is a clarifier). [EDIT] It will only filter out IF it combines with other particles, such as clumping together algal cells. The PolyQuat by itself is too small to get caught in a filter. The Buckman recommendation of shocking with chlorine first to rid the water of organics and algae may be so that the PolyQuat has a better chance of lasting longer in the main body of water since such water will be cleaner and not have particles or algae to consolidate and clump with the PolyQuat (which would then be more likely to get filtered out, as clumps). [END-EDIT]