PolyQuat and Shocking with Chlorine

[chem geek]

Well, I just finished closing my pool today. I had my FC at 4, then added 48 oz of PolyQuat to my 19,200 gallon pool. FC dropped to 0. I then shocked it up, and, today, when I closed, FC was 13.5. I used Liquid Chlorine.

The 48 oz in 19,200 gallons is equivalent to 25 oz in 10,000 gallons so 2.5 times the example I calculated earlier. So I would expect this PolyQuat to consume 2.5 * 2.2 = 5.5 ppm of chlorine so it is not surprising that it consumed all of your 4 FC. In theory, it would have consumed another 1.5 ppm of the amount you added to shock, though you've said that you didn't notice this when you then added chlorine to shock level, though 1.5 might not be that noticeable when shocking to 13.5 (it's a 10% error).

[CarlD]

The 48 oz in 19,200 gallons is equivalent to 25 oz in 10,000 gallons so 2.5 times the example I calculated earlier. So I would expect this PolyQuat to consume 2.5 * 2.2 = 5.5 ppm of chlorine so it is not surprising that it consumed all of your 4 FC. In theory, it would have consumed another 1.5 ppm of the amount you added to shock, though you've said that you didn't notice this when you then added chlorine to shock level, though 1.5 might not be that noticeable when shocking to 13.5 (it's a 10% error).

That all adds up. I probably would have had FC of 15ppm.

The next question (and Buckman may answer it) is whether PolyQuat and Chlorine are working together or fighting. Is there a residual that PQ leaves that continues to be effective against algae growth? Or is it gone?

(BTW, if this gets more technical I'll move it to the China Shop.)

[chem geek]

(BTW, if this gets more technical I'll move it to the China Shop.)

Perhaps you didn't notice, but we are already in The China Shop! I started the thread here because I knew the issue was controversial and not for newbies, though I wasn't sure how technical it was going to get (of course, I tend to make things go that way... ).

And your point is quite valid of whether the chlorine breaks down PolyQuat, thus defeating the purpose of using it, or if it combines with PolyQuat to form a potent compound to inhibit and kill algae. Hopefully we'll find the answer to that soon.

Richard