Trichlor and CYA

[Cherie]

Split from trichlor-and-cya-t14385.html Butterfly

Jason, I have a question on the trichlor. I'm low on CYA, although I'm really not losing much FC during the day. I have 3 3" 8 oz trichlor pucks left from when we had our pool installed last year. I've read where folks have used those to bring their CYA up. I can't figure out how much it will bring it up though and in what amount of time.

I read that one puck raises FC by 10 and CYA by 6. Is that the TOTAL amount that one 3" puck will raise it - over the course of a week or two, thus, one puck renders appx 1ppm FC daily? I've been keeping my CYA at 20 since winter and losing very minimal FC daily - so want to keep it that low. Right now, due to rain dillution, I'm at about 15ppm and have been keeping my FC at 2ppm daily with bleach, until I decided to toss the pucks in to raise my CYA. But I put in all three of the pucks, expecting an FC of 3ppm in the a.m. and my FC this morning was still only 2ppm (7am) and 1.5 (7pm) - and yesterday morning, was 2. Those figures are still safe, given how low my CYA is. But shouldn't the FC have been higher? I need to know how much FC each puck will add DAILY.

I'd like to keep my CYA at 20-25. So is it safe to assume that using all THREE pucks will raise it from 15ppm to 33ppm? 6x3=18 and 18+15=33! Am I right on this? If so, I'll remove one of them.

It's a bit scary getting off my routine! I've only had to use stabilizer and baking soda once, when we had the pool installed last May. And when my CYA was at 20, I was only having to use 1 qt or less of 10% daily. I added 1 qt of 6% tonight just to be on the safe side. Current readings before adding bleach tonight (with pucks still in pool):

FC 1.5
CC 0
pH 7.3 (pucks lowered it from 7.5)
TA 70 (went up a few days ago from 60, which is what I've been keeping it at)
CYA 15

Sorry for threadjacking, but I figured if someone else is looking for low CYA info, it would be good to have as much info as possible in one thread!

Thanks.

 

[PaulR]

I read that one puck raises FC by 10 and CYA by 6. Is that the TOTAL amount that one 3" puck will raise it - over the course of a week or two, thus, one puck renders appx 1ppm FC daily?

No no, the 10 and 6 is the ratio of FC to CYA; it's not the total ppm. So if you add enough trichlor to raise FC by 5, you would also raise CYA by 3.

You can use the "effects of adding chemicals" section near the bottom of the Pool Calculator to figure out how much FC and CYA you'd get from 24 oz trichlor. Make sure to enter your gallons at the top first.

Most likely you won't get much though; you'll need to get some real stabilizer.
--paulr

 

[JasonLion]

Usually, you don't want to use trichlor to raise the CYA level, both because it is too slow, and because it will lower the PH dramatically. The major exception is a fresh plaster startup, where the PH needs to be lowered.

 

[Cherie]

"Most likely you won't get much though; you'll need to get some real stabilizer"

Yes, Paul, you're right. I checked it this morning and the CYA really hasn't budged after four days of pucks! So I guess I'll be doing the sock thing!

Thanks Paul and Jason.