Using trichlor tabs to bring up CYA?

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pleasantpool

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Mar 30, 2014
20
Hudson valley NY
Hi all,

I've managed to SLAM my pool into a good state after opening earlier this month, but my CYA is still kind of low. (It's ~20ppm for my 18700 gal). I'm low on pure CYA, but I have a bunch of 3" trichlor tabs that I figured I could use to bring it up.

The tablets say they are 93.6% trichlor, 2.5% zinc sulfate monohydrate, and 3.9% "other", which is where I guess the CYA is hiding.

I added two 3" hockey pucks to my floating tablet holders. Any idea what kind of increase is to be expected for FC and CYA? FC pre addition was 2ppm and CYA was ~20ppm.

Thanks,
 
Take a look at the effects of adding chemicals section at the bottom of Pool Calculator to see how they will affect the water, and watch out because they lower PH.

Trichlor adds CYA fairly slowly, but will eventually get there.
 
The CYA is actually within the 93.6% 1,3,5-Trichloro-1,3,5-triazinane-2,4,6-trione component.
The zinc stuff is an algaecide. Too much of the zinc in the water can cause metal stains
The "other" is probably clay used as a binder

Trichlor is very acidic. If your pH or TA are towards the low end, you could drive pH too low.

Plug all your values into poolmath and then scroll down to where it says Effects of Adding Chemicals and see what each 7 oz puck will do to your chemistry.
 
Ah, I didn't know about that drop-down at the bottom. Assuming a 3" puck weighs 8 oz (which someone claimed online), 2 pucks would raise my FC by 5.9 and CYA by 3.6 .... meaning I need to use about 11 of those pucks to raise my CYA all the way.

Do trichlor pucks go bad? Mine have been sitting in the garage from the previous owners for at least a year.

Also, any guidelines for CYA target in the northeast? (I'm in Hudson Valley NY)... Sounds like people down south with lots of sun keep the CYA pretty high but not sure what to target mine. I picked 40 but that was arbitrary. Basically minimizing chlorine usage while also minimizing daily loss as much as possible.
 
Also, any guidelines for CYA target in the northeast? (I'm in Hudson Valley NY)... Sounds like people down south with lots of sun keep the CYA pretty high but not sure what to target mine. I picked 40 but that was arbitrary.
Click to expand...
40 is what I would have suggested for your climate.
 
pleasantpool said:
Ah, I didn't know about that drop-down at the bottom. Assuming a 3" puck weighs 8 oz (which someone claimed online), 2 pucks would raise my FC by 5.9 and CYA by 3.6 .... meaning I need to use about 11 of those pucks to raise my CYA all the way.

Do trichlor pucks go bad? Mine have been sitting in the garage from the previous owners for at least a year.

Also, any guidelines for CYA target in the northeast? (I'm in Hudson Valley NY)... Sounds like people down south with lots of sun keep the CYA pretty high but not sure what to target mine. I picked 40 but that was arbitrary. Basically minimizing chlorine usage while also minimizing daily loss as much as possible.
Click to expand...
Pucks are either 7 or 8 oz, generally. Weigh one on a diet scale or a postage scale and see what you have. I went with 7 oz, since they're only 93% pure.

Did you also note the pH drop each puck causes?
 
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