Can cya go down that fast?

[DanS]

I struggle to read the level correctly for my cya test using drops, but these numbers from a pool store look close to what I got:
May 30 - CYA 99
Aug 30 - CYA 80
That drop in the number seems reasonable to me. I didn't need to backwash, but a fair amount of water was added via the hose or rain water. Here's what I don't get.
My pool service added cya each year for the past 5 years, and they claim that they get a reading of 0 at the beginning of the year. My pool is 20,000 gallons, and I understand that 16 lbs. of CYA would raise it from 0 to 100.

The pool company says they added 16 lbs in year 1, 15 lbs year 2, 8 lbs year 3, 12 lbs year 4, and 20 lbs year 5. Could this be possible? If I lost half of my cya each year, which seems high to me, my reading this year would be about 200. Am I missing something, or should I look for a new pool service company?

[CarlD]

IMHO, I would say the latter. Buy a good FAS-DPD test kit and measure all these things yourself. The $60-$80 it costs you will be far, far cheaper than the service. Take 2-5 minutes a day to test and adjust your water and you'll wonder why you EVER used a service. Splurge on a robotic automatic pool cleaner and you'll never need a service again.