Aeration / CYA level in SWG pools


In The Industry
Jun 20, 2016
I have two different questions I'm hoping someone can shed light on for me. First is regarding using aeration to raise pH:

Is it true that aeration only raises pH up to about 7.5, then has little effect after that? I remember reading that in a post here. If that is true, why do SWG's raise pH up much higher than 7.5? Isn't it supposedly aeration from hydrogen gas produced during the process of chlorine production that causes the pH rise?

Second question:

I also remember reading that after CYA is raised to 50ppm, there is really not much benefit as far as protection from UV degradation. If that is the case then why is it recommended to keep CYA higher with a SWG? Is there another reason other than the UV protection? Is it for CSI? Or am I just wrong and there is much more benefit being higher than 50ppm?


LifeTime Supporter
TFP Guide
Apr 2, 2012
Columbia SC
I'll take a stab at both and get corrected if I'm wrong :)

Yes. And SWH will continue to raise PH ....BUT......that can depend on your TA level which acts as a buffer for PH swings. I run a SWG and I'm one of those (seemingly rare) folks that doesn't fight PH rise from the SWG as I keep my TA in the very lower range of reccomended and seem to have found that sweet spot.

Higher CYA reccomendation with SWG has to do with the fact that you are essentially constantly adding small amounts of chlorine all the time while SWG is running instead of large doses. The higher CYA helps protect that chlorine from sun consumption before it can help sanitize your pool.

I'm sure there is a more complex scientific answer to those questions but that is my regular person summary :)


Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
Aug 10, 2012
Aeration can raise PH well above 8.0. Any type of aeration causes carbon dioxide to out gas from the water and raise PH.

No, there is no cap of CYA at 50 ppm. I noticed a pretty significant increase in FC protection when I went from 70 to 80. That is why we suggest higher CYA levels for SWGs, and higher in southern climates.

Add your pool info to your signature so that we can help you better. More here, Pool School - Read This BEFORE You Post