CYA going down by itself. How is this possible?

[Tabaan]

Hi!

I have a quick question, I am left a little confused.

I have a new pool, 15 000 gallon inground, opened it in May.
It's been fantastic, no issues (I opened in in May).
We use stabilized chlorine sticks in the skimmer (have a UV-system as well). Weekly visits from a very reputable pool company.

In early June the CYA was a bit high (85) and I assumed this would get worse with each chlorine stick added and planned a partial drain.
I add 1 stabilized chlorine stick every week, and the pool guys shock every other week. Pool is crystal clear, always.

The pool guys also take a water sample every week.

Now, after three months of daily use the CYA level is....67? Down from 85. I was expecting it to be in the hundreds.
How is that even possible?

I know CYA does not evaporate.
I do lose quite a bit of water due to heavy use/kids splashing too. I add about 2-3" of fresh water every week.
The pool lab tells me this must be why CYA is down, that I end up topping up with more fresh water than stabilizer. Does that make sense to you guys, anyone have similar experiences?

Oh and there are no leaks. If I leave the pool covered the water level doesn't drop at all for days.

Thank you in advance for any advice!

[Denniswiseman]

2-3" of fresh water every week is a partial drain and refill. If you are happy with the cost of the water, you've solved your CYA problem