CYA vs chlorine ratio question


Active member
May 23, 2021
Long island ny
New member here... First year trying to actually understand my pool. Spent the first 6 years using pucks and ended up with 136ppm cya last season.

Drained most of the water and I'm sitting at around 48ppm this year and my pool is about 7600 gallons. (18ft round above ground)

I'm using the app and it suggests to keep my FC at 4-8ppm (ideally 6ppm) with a cya level of 48. Everything else Ive seen says normal cya levels are 30-50ppm and FC should be 1-3ppm.

Pools been open for about a week and I've been testing the water every day getting a feel for my new testing kit and using 12.5% bleach as my sanitizer. Everything looks good and I'm only adding 16-20oz a day to maintain 6ppm. I'm just wondering if I really need to maintain 6ppm or if I should be in the typically recommended range of 1-3ppm.

I understand that if cya level is high, then you need a higher FC level to have the same effect. But my cya is within range. A little confused and just want to make sure the FC isn't too high for the kids.


Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
Laughlin, NV
Pool Size
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
The FC/CYA chart is based on the % of CYA your FC needs to be to keep your pool sanitary and clean. TFPC has found that when using liquid chlorine, 7.5% of CYA is the minimum the FC should be allowed to be. So the target ranges are higher than that so it accounts for daily loss of FC.
The active chlorine in your pool water with a CYA of 50 ppm and a FC of 6 ppm is a fraction of that in public pools with no CYA, and even most tap waters.
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