Confused about CYA levels

I have been balancing my new pool water and I am finally ready to add CYA, but I am confused as to what level I should target. I have a SWG, and have been reading that 70 to 80ppm should be the target, but I thought that at higher amounts of CYA, chlorine becomes ineffective. Also my TA is still at 120 (down from well over 200). Will this have an impact? Please advise

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Tonight's testing showed
ph7.8, TA 120, FC 3.6, CC .2
CH 360.

CYA currently at 0


Well-known member
Aug 16, 2014
Northern IL
Adding CYA will slightly lower your pH and therefore the TA. Add CYA at a half-ish dose and retest a few days later. Its is better to undershoot CYA additions than to overshoot. Sometimes people have their pool volumes wrong or something else.
Please use a 10ml water sample for FC/CC in the future and multiply your drops by 0.5 instead of 0.2.


LifeTime Supporter
TFP Expert
In The Industry
May 20, 2007
SWSuburban Chicago, IL
Have you read water balance for SWGs in Pool School? It explains the CYA question you have. Actually without it you are on the high end and should add at least 30ppm now. What % is your SWG running at?

The TA will cause the PH to creep up, every time it hits 7.8, use muratic acid to lower it to 7.2. Eventually (without water addition) the TA drops into range and the drift slows or stops. In arid climates with necessary water addition, it may be an ongoing thing... but other than that the high TA won't hurt anything. Keep the PH in range and you'll be fine.


Mod Squad
LifeTime Supporter
Platinum Supporter
TFP Expert
Aug 10, 2012
CYA and TA have no effect on each other. With that hot Las Vegas sun I would put your CYA at 80 ppm. Higher CYA doesn't make chlorine ineffective, you just need to keep chlorine at the correct level based on the CYA level and the Chlorine CYA Chart. Keep it at target at all times and never let it drop below minimum and the pool will stay sanitary and algae free.

Feel free to add some bleach from time to time to help the SWG keep up with extra demand. I usually add a jug before and/or after big swim parties or big swimming weekends.


LifeTime Supporter
TFP Guide
Gold Supporter
Jul 3, 2013
Fletcher, OK
Welcome to TFP :)

Yes, we recommend 70 to 80 CYA for SWG, mine is at 80 now.. chlorine doesn't become ineffective you just need a higher FC amount..

This allows the SWG to be run at a lower level than a normal pool because you run the pump longer and the chlorine is constantly being added to the pool.. below in my sig is the recommended levels..

you can add the amount to get to 70 CYA in a sock, I used long john's :) it is a lot of CYA to go to 70, the trick is to kneed the CYA so it dissolves into the water faster, once all gone wait 24 hours to test again..

I hope this helps :) here is proof

Thanks everyone for your help. CYA added today via knee highs...worked great. Quick dissolve and dispersion into the pool. Will recheck levels in a day or two and I also got some chlorine bleach to add if my FC is too low for the CYA level!!!