Trying to lower CYA - do the Member's Mark Tabs have stabiizer?

[Dubb]

This is my first post, wish I had found you guys years ago. This is my 5th year with my pool and the previous 4 have resulted with algae in late summer. I've used multiple test kits, strips, apps and weekly trips to the pool supply store to no avail. After reading pool school and many posts I was shocked to learn how important CYA levels are. Last year I spent most of my summer at the pool store getting water tests and they never mentioned it, guess I shouldn't be surprised. My latest goof was using the Clorox pool app and strips. You take pics of the strips with your phone and it recommends levels of chems. It was way off kept telling me to up my PH and stabilizer. This was a few weeks ago and looks like the PH is back down but the stabilizer is still 100ppm, that's after draining down past the skimmer and replacing. I tested today using the TF-100 and got the following:

FC = .25
CC = .05
TA = 140
CYA = 100
PH = 7.2

I know the FC is way too low but I was gone for a week and had not put any new tabs in.

My question is can I continue to use the Members Mark Chlorinating Tabs or will they keep my stabilizer high? It says a stabilizer should be added when using so that lead me to believe it didn't have any but I've read on here that most tabs do. The tabs are Trichloro-s-triazinetrione. Please tell me the "s" doesn't stand for stabilizer. I use them in a floating dispenser. My water is very clear for now but that usually changes in the next few weeks. Thanks.

 

[Donldson]

Welcome to TFP!

Well... No, the S does not stand for stabilizer. BUT, trichlor is stabilized chlorine. The more common name for trichlor is Trichloroisocyanuric acid (emphasis mine). For every 10 ppm FC added by trichlor 6 ppm CYA is also added. There is no way around it, continued use of tablets in your pool will only continue to increase your CYA. Doesn't matter the manufacturer, trichlor raises FC and CYA. This is almost definitely why you seem to deal with algae in late summer, and you aren't alone. We see such year after year.

The best thing you can do is remove the tablets and replace water to bring your CYA down. When you did the CYA test did you get right to the 100 line or did the dot disappear before it ever reached the line?

 

[Dubb]

Welcome to TFP!

Well... No, the S does not stand for stabilizer. BUT, trichlor is stabilized chlorine. The more common name for trichlor is Trichloroisocyanuric acid (emphasis mine). For every 10 ppm FC added by trichlor 6 ppm CYA is also added. There is no way around it, continued use of tablets in your pool will only continue to increase your CYA. Doesn't matter the manufacturer, trichlor raises FC and CYA. This is almost definitely why you seem to deal with algae in late summer, and you aren't alone. We see such year after year.

The best thing you can do is remove the tablets and replace water to bring your CYA down. When you did the CYA test did you get right to the 100 line or did the dot disappear before it ever reached the line?

Thanks, I'll do just that and hopefully have a good update in a few days. I appreciate it. I slowly added the drops while looking in the tube and when I couldn't see it I stopped and it was right on 100.