New SWG unable to keep PH in check

[Crani07]

Just put a new Hayward SWG to my 27k vinyl pool. Works great. Unable to keep and maintain correct PH. After about 5 days of it being balanced will trend to over 8.
FC 4.5
CC 0
Alk 80
Ca 70
Cya 50
Saturation index 0.2

I know my cya is on low side so slowly adding more. When I go to correct PH it only requires about 2 quarts of muriatic acid and will get me back down to 7.4. Is it all because of my low cya levels? Any thoughts.
First time posting so let me know what I'm missing.
Thanks this site is great

 

[ping]

SWG's tend to make the pH rise due to the aeration the SWG makes. Lowering the TA down to 60 should help slow down the rise in the pH.

 

[Crani07]

Thanks. Will just give it time to let alk lower on its own.

 

[ping]

That may or may not work depending on how much fill water you add and what the TA and pH are of the fill water.

During the winter I can easily drive the TA down in my pool as I add very little fill water, but right now I have to actively lower the TA to drop it.

 

[Crani07]

Good point. Will add acid and try to get it balanced that way.
Thanks again
Mike

 

[txnole]

SWG pool here. One tip might be to increase your CYA to lower your TC loss daily and thus dial back your SWG run time. Regardless, you are likely to be adding acid with some regularity.

 

[Crani07]

Yes slowly increasing cya trying to get it closer to 70. And yes lower run time of generator.