Strange test results -- very high combined chlorine (CC)

[PoolDoc]

Sorry I hadn't picked up on this sooner.

You are almost certainly experiencing the well-established problem of cyanuric acid conversion to ammonia or urea by bacteria. This results in the HUGE chlorine demand, and high CC levels, you are seeing. There are only two solutions: (a) drain and refill - NOT safe on vinyl IG pools, OR (b) chlorinate until the demand is gone.

You can use the bucket test BigDave described to answer, approximately, the question, "How much more chlorine will it take?". Or you can just chlorinate till it's done.

For a variety of reasons, you are probably better off doing this at a higher than normal pH, but you can't go very high with Alk and CH over 300 ppm. So, I'd recommend using borax to push the pH to ~7.6, and holding there till you get the situation under control.

Do NOT swim while you are doing this. High chlorine is rarely a problem for people, but high chloramine levels are something different.

Adding CYA will slow the process at this point. My recommendation would be to
1. Use borax to raise the pH to 7.6, and hold it there.
2. Dose each evening with 4 gallons of household bleach UNLESS the TOTAL chlorine (FC + CC) is greater than 20 ppm. Skip doses when TC levels are above 20 ppm.
3. Use the bucket test if you want to find out how much longer you have to go.

Sorry about this. We had many, many cases last year, with the super-warm spring of 2012. This year, with a record cold spring, there have been very few cases.

[Leehicks79]

Scoop of powder (turns red). Count drops of 0871 until it stays ...

Shouldn't it be TWO scoops of powder?

[BigDave]

if it turns pink, one is enough.

[Themadczar]

Ok, thanks. At least i know what I'm dealing with. However I have added 5lbs of dichlor in the last few days... My cya should be around 23 (I'll test tonight unless it takes longer to fully dissolve and I would just be wasting reagents). Does that change your recommended evening dose of chlorine, PoolDoc?

[PoolDoc]

Not really.

CYA may slow the reaction of chlorine with ammonia, but not by much.

[Themadczar]

Added 1 cup of borax to the skimmer... Will check ph tomorrow night and act accordingly. And 4 gal of bleach will be going in shortly, then I will check tc tomorrow night as well. Thanks for the help. I'll let you know if anything else comes up.

[Watermom]

By the way in case we haven't said it before, thanks for the subscription. We appreciate the financial support to keep this forum alive!

[Themadczar]

One more question... How do I know when the process is complete? Cc down to 0?

[Watermom]

Yes, and no more than a 1ppm drop in chlorine from sundown one evening to within one hour after sunrise the next day plus having clear water. We then usually recommend holding the chlorine high for one additional day for added insurance and then let it drift down and keep it in the appropriate range based on your CYA level.

[Themadczar]

Update...
Still feeding the chlorine demand. 5# of dichlor and 39 gal. of bleach (or about 162ppm of chlorine) so far. Just got back from a week long vacation, and things are no worse than when we left. I had our friend who watched our dog dump in partial doses (1-2 gal of bleach per day) while we were gone. FC last night was 5.0 and CC was 18.5. I will continue to chlorinate. Hopefully we are nearing the end. We would like to swim this summer. :-/
(I decided not to waste my time/reagents on the bucket test. The results don't change anything. It will be done when it's done.)