Moved to Kansas last year and got my first in-ground pool. Once opened this Spring I did a full battery of tests and CYA was ~40.
My previous experience is 3.5 years with an 8000 gallon vinyl AGP, using BBB method with occasional dichlor. Pool was generally stable once opened each Spring, and I rarely performed the full battery of tests except for PH and chlorine weekly. I normally kept CYA at 40-60...if anything it went UP over the season.
Back to the 'new' pool- I've noticed I've been using a LOT of chlorine lately, and over the past two weeks the pool has been used daily. I realized I haven't run a complete panel of tests in a couple months and haven't checked PH in a couple weeks. I've been using mainly 10% liquid CL, some Cal-hypo and occasional trichlor puck.
So...today we have (K2006 test kit)
PH 8.0+ tested twice
CYA 0 ???? tested twice, second time with new reagent
My understanding is that CYA doesn't just "go away". I would expect to lose a little with backflushing the sand filter, but zero? Could the test be incorrect due to high PH? The pool water + reagent was CLEAR.
I realize the main problem is I've been lazy with my water testing and just dumping Chlorine in. Need to check CYA as well as PH and chlorine at least weekly.
I was estimating my pool at 18000 gallons. Recalculating today it's probably closer to 20000, possibly more, I'm not sure exactly "how deep the deep end is"... So I may have been underdosing chlorine.
I added 23oz of muratic acid to bring the PH down, and 1 gallon of 10% CL and 2 lbs of cal-hypo (was out of liquid). Also put 3 trichlor pucks in the floater.
Picked up more liquid as well as CYA today and will reassess in the morning. Working till 11PM so not much more will get done tonight. May add a partial dose of CYA when I get home.