Can CYA be "disappeared" by AA and/or Jack's Blue Stuff?

[Chuck_Davis]

I had my pool nicely balanced, with CYA at 50. I normally keep my FC at 2-3, with Borates. I then did an AA stain treatment, including 3 bottles of Jack's Blue Stuff as sequestrant. The Blue Stuff got up to around 18 ppm.

A couple of weeks later, when I tested CH, CYA and Borates, my CYA was barely registering on my TF test kit. (Followed by a thankfully minor algae breakout.) Other than a bit of rain and a couple of backwashes, there wasn't any significant dilution of the pool. The pool did turn milky after the AA treatment, which is normal, but filtering and clarifier took care of it.

The only other unusual factor is that I changed the zeolite in my filter after the AA stain treatment. (It was due to be changed anyway, so I figured I'd be certain to get rid of all the metals that were lifted, sequestered and filtered.)

I'm bringing the CYA back up, but I'm curious if it was the AA and/or Jack's Blue Stuff that disappeared the CYA and, if so, why. Is there anything else that can eat CYA? Is there any chance the reagent for the CYA test suddenly went bad and the test results are incorrect? (It was fresh this spring.)

 

[JoyfulNoise]

Neither AA nor Jack's Magic Blue Stuff (HEDP sequestrant) will affect CYA. It is also unlikely to be related to a "bad" reagent, the R-0013 almost never goes bad and I have used 2 year old R-0013 before which gave exactly the same results as a fresh bottle.

The only thing that reduces CYA is water exchange. If you had a water leak, then you can expect your CH, borates and CYA to all decrease in roughly the same proportion. Any water leaks?

 

[Chuck_Davis]

No leaks, and CH and Borates held. That's why this is a head-scratcher.

 

[frustratedpoolmom]

Curious, what your FC and CC readings were during this time? CYA can convert to ammonia, have you been struggling to attain a FC reading during this process?

 

[Chuck_Davis]

No problem with FC or CC.

I was still tuning the Liquidator for the season (and after jiggering flow rate with the zeolite change and putting the heater back in-circuit) and FC got a little low which (in conjunction with the low CYA) allowed the algae breakthrough. One jug of chlorine fixed that problem, though.

This may just end up as another entry in the annals of Weird Pool stuff!

 

[pooldv]

Bacteria consuming the CYA is really the only possibility. And that can only occur with low FC below minimum for your CYA. With CYA of 50 your target FC is 6 and min is 4, so 2-3 is well below min and AA and sequestrant can both consume FC. Chlorine CYA Chart