Chemistry Advice on TA and CH

[vnkt0207]

I just bought a house and inherited a salt pool with poor chemistery.

FC = 9 (was as high as 11)
CYA = 40
pH = 7.5
TA = 110
CH = 280
Salt = 3200

I am in the process of raising the CYA to around 80. pH was too high originally at over 8 so I quickly lowered it to 7.5 with acid. I am lowering the Aqua Rite SWG % output to get to FC of 6. Right now, TA is too high and CH is too low. But are these two levels a concern? It would seem so (for TA) based on the notes I read of TFP in the SWG section. Thank you for hte advice.

 

[mas985]

CSI is about perfect for a SWG pool so I wouldn't change a thing. It is the combination of PH, TA and CH that matters more to scaling and corrosion than the individual components although you shouldn't let any one component get too far out of range. Plus, if you have hard fill water, CH may climb over time anyway and then you will need to bring down TA some.

 

[pooldv]

With TA at 110 your PH will probably tend to rise. Adding acid to lower PH back to 7.5 or so will slowly lower your TA. It is important to keep PH at 7.8 or lower.

More on lowering TA here, Pool School - Lower Total Alkalinity

More on basic pool chemistry here, Pool School - ABCs of Pool Water Chemistry

More on saltwater pool chemistry here, Pool School - Water Balance for SWGs

 

[chem geek]

If you are lucky enough to find your pool's pH being stable at the current TA, then of course there's no need to change it. If you do find the pH to rise over time too quickly for you, then you can add acid which will lower both the pH and over time the TA should drop (unless you've got a lot of evaporation and refill). If the TA drops over time, you can target a higher pH (say 7.7) if that becomes more stable.

Basically, if it ain't broke, don't fix it, so just see how your pH goes. It's possible it's OK where it is though that would be unusual for an SWCG pool.

 

[mas985]

Also, if you were to target a low PH of 7.2, post acid dosing, it would keep your CSI around -0.5 which would help keep scale off the SWG plates and it would also slowly drop TA. I just think adding CH to an SWG pool is unnecessary unless it is really low (<200 ppm). CH is usually hard to keep down for most people so I think it is much better to manage PH and TA to keep CSI in check.

 

[vnkt0207]

Thank you all for the advice.