Is it possible to have zero Combined Chlorine even though organic matter in pool?

[jdlw]

Opened our pool 1 1/2 days ago and am currently in the thick of SLAM. While I'm maintaining free chlorine at the levels indicated, I am getting a zero reading for combined chlorine. Even yesterday when there was still all kinds of guck in our pool. I have tried it multiple times over the past day and a half and still getting zero. Have never ever seen a zero withing 6nhours of pool opening - especially since we were still vaccuming and brushing over winter stuff out.
My husband went to pool store which showed combined chlorine of 3 yesterday and a little over 2 today - which makes more sense. But I know we aren't supposed to rely on pool stores. My R-0003 has an expiration of April 2024, so it should be good. I store it indoors in a cool spot away from light - do you think the issue is with the -0003? Weird. I guess I"ll have to try a store that carries the R-0003 since I can't wait for the shipping if I order online through the place mentioned here (plus not a big enough order to make shipping worth it). Any ideas why R-0003 would go bad before the expiry if that is what happened?

 

[PoolStored]

Yes, CC=0 is common, even during SLAM.

 

[Mdragger88]

Reagent could be bad but the absence of cc’s during slam isn’t necessarily uncommon. Just like the absence of cc’s doesn’t mean everything is fine either. That’s why there’s multiple criteria for ending/ determining need for the
SLAM Process.
The presence of elevated cc’s however always indicates a problem.
The pool store’s testing stuff could be dirty.
Get a new bottle and go from there.

 

[tikoh]

Yes, CC is formed when chlorine (specifically hypochlorous acid) combines with nitrogen or ammonia for form amines. Algae does not have a lot of nitrogen or ammonia, these substances are found in proteins, sweat, and urine. CCs are usually (but not always) a sign of high bather load rather than an algae issue.

See #8 here: CC - Further Reading