CYA loss?

[napkin41]

So I've been lurking for a while, I feel like I have pretty good control of my chemistry. That being said, I have the most difficulty with CYA. I feel like it's really hard to "pin down" a solid measurement using the TF-100 kit. My pool has been riding at what I'm pretty sure was 40-50 CYA for a couple months. I measured again just today, and for the first time I feel pretty strongly that it's about 20-30.

I was under the impression that CYA is one of those compounds that doesn't "go away" unless you drain and refill the pool. (I've also read some arguments that CYA will go down during the winter when the pool is closed and covered because of organic material and science and whatnot.)

So my question is, is there any mechanism for CYA to lower in the spring-summer time? (I have been refilling the pool, but it's been pretty hot in North Texas. I'm pretty sure I don't have a leak.)

Thanks!

 

[Donldson]

CYA is broken down by chlorine, but extremely slowly. On the scale of 2-5 ppm/month for typical pool FC and temperature. I think we have seen up to around 10 for people who keep their pools especially warm, and sometimes more than that in a hot tub.

So between that natural decay and the margin of error for the CYA test (we know, unfortunately it is the best consumer grade test available) I would say your results are not unexpected.

 

[napkin41]

Thanks for the reply Donldson. That does make sense. I'll keep that tucked away in my back pocket!