FC at pool closing

[run53]

I was wondering if it is a good idea to get the FC up to SLAM levels for closing. At the moment, I am at FC=8.5 with CYA of 70. I was thinking of bringing FC up to 20, then add 1 qt of poly 60, then circulate for a few hours before closing. Any harm or benefits to doing this?

 

[BoDarville]

No only is their no harm in doing this, it's actually recommended (although FC SLAM level is 28 ppm for a pool with a CYA of 70 - see Chlorine CYA Chart). Only tweak is to first bring FC up to SLAM level, then add the polyquat60 after FC falls about half way back to normal levels.

Here are the closing guidelines:
Closing an In Ground Pool
Closing (Winterizing) Your Above Ground Pool

 

[run53]

No only is their no harm in doing this, it's actually recommended (although FC SLAM level is 28 ppm for a pool with a CYA of 70 - see Chlorine CYA Chart). Only tweak is to first bring FC up to SLAM level, then add the polyquat60 after FC falls about half way back to normal levels.

Here are the closing guidelines:
Closing an In Ground Pool
Closing (Winterizing) Your Above Ground Pool

Thanks, but I'm a bit confused. When I plugged my numbers into the Pool calculator, it told me that shock level is 20.

 

[BoDarville]

Their are some discrepancies between the Chlorine / CYA Chart and the Pool Calculator. The short answer is that either one is correct. The FC numbers for SLAM levels are targets, not absolute minimums. The chart is just a bit more aggressive. If your pool is clean and algae free, the 20ppm level will work fine for closing.

 

[run53]

No only is their no harm in doing this, it's actually recommended (although FC SLAM level is 28 ppm for a pool with a CYA of 70 - see Chlorine CYA Chart). Only tweak is to first bring FC up to SLAM level, then add the polyquat60 after FC falls about half way back to normal levels.

Here are the closing guidelines:
Closing an In Ground Pool
Closing (Winterizing) Your Above Ground Pool

I'm curious about this. Why is it important to let the FC levels drop half way to normal before adding the poly60? Is it something with the reaction to poly60? In past years I would bring my pool to shock level on the same day as closing (but never used poly60).

 

[chem geek]

Yes, chlorine oxidizes Polyquat 60 though it mostly breaks it up into smaller pieces that are still effective, but eventually it breaks down further and becomes ineffective. So the Buckman Labs (makers of Polyquat) procedure recommends lowering the chlorine level after shocking before adding the Polyquat. It will lessen the amount of Polyquat that is degraded (half the FC level will degrade the Polyquat half as quickly) but should still be enough to get through the winter if the water is very cold.

It is not a disaster if you add the Polyquat at shock levels of chlorine. You'll just see the chlorine level drop more quickly and some of the Polyquat will have been oxidized as a result. It's just less than ideal.

 

[run53]

Yes, chlorine oxidizes Polyquat 60 though it mostly breaks it up into smaller pieces that are still effective, but eventually it breaks down further and becomes ineffective. So the Buckman Labs (makers of Polyquat) procedure recommends lowering the chlorine level after shocking before adding the Polyquat. It will lessen the amount of Polyquat that is degraded (half the FC level will degrade the Polyquat half as quickly) but should still be enough to get through the winter if the water is very cold.

It is not a disaster if you add the Polyquat at shock levels of chlorine. You'll just see the chlorine level drop more quickly and some of the Polyquat will have been oxidized as a result. It's just less than ideal.

Thanks. That explanation helps a lot as this is the first year I'm using Polyquat. Might as well just do it right