During my recent water testing, I was so surprised to see CYA was over 100. I really don't know why because I stopped using Tabs months ago, and the rest 4 chemicals I have ever put into my pool so far are:
1) (powder) Granular of LeisureLiving, 99.3% of Sodium Dichloro-s-triazinetrione dehydrate, relevant amount used every week after a water test.
2) Chlorinating Liquid of KEMTEK, 10% of Sodium Hypochlorite, relevant amount used after a water test, only used about 4 or 5 times when needed, all before I had received the Granular.
3) (liquid) Muriatic Acid of KEMTEK, 14.5% of Hydrogen Chloride, relevant amount used after a water test, only used about 2 or 3 times when needed.
4) Regular 20 Mule Team Borax, relevant amount used after a water test, only used 3 or 4 times when needed.
That is, none of above 4 chemicals has anything to do with high CYA, right? And in last 2 months, I only put Granular powder into the pool since other chemicals were balanced.
A little more contexts: I had my vinyl replaced in mid of last Dec, so I had the opportunity to start with a whole pool of fresh water. I know certain CYA is "helpful" to hold chlorine accountable, so at the beginning, I used the 3" Tabs of aqua chem, which had 94.05% of Trichloro-s-triazinetrione. When CYA reached about 50, I stopped using it, it was in this Apr timeframe or so. I didn't test CYA anymore without Tabs.
I tested CYA twice in last 7 or 10 days, I really don't understand why CYA is 100+. How could that be? My latest water test result in this morning:
Cal. Hardness: 110