CYA to FC Correlation

johnsonatx

Member
Mar 31, 2017
14
Austin, TX
Currently my CYA is 50 and I've been pouring about 64oz of 12.5% bleach in daily to keep FC at 6 (14,500 gallon concrete pool). It seems a lot to me but maybe I'm just not used think liquid chlorine stuff as I just switched off pucks a couple weeks ago. All my other chemistry numbers are in check and water is crystal clear. When I have been checking every morning I am getting FC reading of only 1 which means I am losing 5ppm every day. That seem plausible? I would like to only be adding every other day as every day is kinda of a PIA, the pucks did have that going for them. Also with high CYA will the FC still show up on test even though it's not being used because of so much stabilizer of does the high CYA cancel out those FC readings?

Thanks for your help
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
11,317
Bedford, TX
J,

We usually say that pool uses 2 to 4 ppm of chlorine per day. Your 64 oz of 12.5% chlorine adds 4.3 ppm to your pool, so you are on the high end..

As Bob suggests, I'd do an OCLT just to be sure it is the sun and not something in the water eating your chlorine..

What you are finding out is exactly why a lot to TFPers are using a Stenner pump system or Saltwater Chlorine Generators...

Thanks for posting,

Jim R.
 

johnsonatx

Member
Mar 31, 2017
14
Austin, TX
Thanks I will try the OCLT this evening, and yes I've been looking at the Steener pumps and automating this process. If I had algae or something else in the pool wouldn't I see it? The water is crystal clear and no complaints minus the excessive chlorine I appear to be using
 

Richard320

TFP Expert
LifeTime Supporter
Jan 6, 2010
20,401
San Dimas, CA (LA County)
Besides running an OCLT, here's a few other things to consider
1) Testing error on the CYA. If you didn't have bright light, the dot will disappear too soon and give you a falsely high reading. I can see a distinct difference in results if I hold the view tube at just the top with thumb and forefinger or if I hold it more naturally with all my fingers touching.
2) The pool is bigger than you think. When you dose with acid or bleach, do you see the results you're expecting or come up short?
3) The bleach is old and not full strength anymore. If you get it at a pool store, there's probably a quick turnover. If it came from Lowes or Home Depot, it could have sat out in the garden center over the winter. Check the date code on the box. https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwjX88jBifLTAhVC7GMKHd2pCgkQFggjMAA&url=https%3A%2F%2Fwww.troublefreepool.com%2Fthreads%2F83147-Chlorine-Date-Code-Decoder-Easy-Way-to-Measure-Strength&usg=AFQjCNEZXCJrWRX5g51X_QDXO-lmXZ6zMg&sig2=aH284ShwM3b8XH92eqK-5Q
 

johnsonatx

Member
Mar 31, 2017
14
Austin, TX
Must of had something in the pool that I couldn't see even though water was crystal clear. I went ahead and slammed it. Took FC up to 20, and after it settled back down to norm I appear to be doing a daily burn of 3ppm. So dropping from 6 to 3 FC per day and dropped my liquid usage from 64oz a day to 44oz. Think I'm good to go now.
 

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