Chlorine ate my Polyquat 60? now have combined chlorine.

[tre]

I've had zero problems with my chemicals all summer. I've never had a hint of combined chlorine. I'm winterizing today and suddenly I have combined chlorine.

What I did:
1) I brought the PH down to 7.4 and added 7 of the 121 oz bottles of Chlorox 8.25% bleach from Costco. Measured Chlorine at 33PPM 5 hours later.
2) Circulated water for 24 hours and added 38 oz of Polyquat 60 as insurance
3) tested Chlorine 24 hours later and it is now at 25PPM with some combined Chlorine.

I have a salt pool with a CYA of 80. I kept my Chlorine at 6-8 all summer and I don't have any algae and never had combined chlorine until today. I think when I brought the pool to shock level and added Polyquat 24 hours later, the Polyquat was simply oxidized and created combined chlorine. My question is now what? I was going to cover the pool today and blow out the lines. Is it ok to do this with the combined chlorine or do I now need to SLAM to get rid of the CC which was created by the Polyquat 60?

 

[JoyfulNoise]

You added the Polyquat too soon after raising your water to shock levels. From the Article on in-ground closing it says -

SLAM - Two or three days before closing, I bring the pool up to shock level and hold it there until FC holds overnight (which it generally does right off on the first night). Then I let the chlorine level fall about half way back to normal levels, typically another day and a half.

PolyQuat - Add the startup (maximum) dose of PolyQuat according to package directions. I give it half an hour to mix with the pump running before starting to drain. While I am waiting for that I proceed with the next three steps.

With that said, I think you're going to be fine. You know that the source of the CC's are from the Polyquat and not for something else. The Polyquat has been degraded a bit, but it will still function albeit perhaps a little less effectively. The CC's are not really going to harm anything and, in fact, act as mild disinfectants themselves. You could leave the pool uncovered for a few days (if possible) and let the sunlight burn them off. Check the CCs regularly to see if they decrease. Other than that, your pool will be fine.

 

[Sparkle]

It is frequently said here that the pump should run for 24 hours after you add the Polyquat.

This post gives a reason for it.

 

[tre]

I followed what Buckman labs told Chemgeek. I believe the problem is that I have a salt water pool which demands higher chlorine levels (due to the higher CYA). Waiting for the pool to fall back 1/2 way to normal level would take 2 weeks at these levels and would likely still have been too high for the Polyquat. I think the simple solution is to skip Polyquat for a salt pool. I'm just going to let the Chlorine do its work.

 

[chem geek]

Or if you want to lower the FC level faster you can add hydrogen peroxide as a dechlorinator. It takes the same volume of 3% hydrogen peroxide to dechlorinate the FC that would be added from the same volume of 6% bleach so you can use PoolMath to determine the equivalent 6% bleach volume for the FC drop you want and then add that volume of 3% hydrogen peroxide. For larger drops or large pools, you can buy 27% hydrogen peroxide in Baquacil Oxidizer and use 1/9th the volume compared to 3%.