My test results 1 month after replastering the pool

[yardoasis]

I replastered my pool a month ago, and the plaster is looking good. We're going into the winter season, however... and the water is quite cold, about 50 degrees. I live far enough south to not have to close the pool entirely, and would use the spa every now and then.

My fill water has high TA and low CH, so I added a little CH to bring it to 200 two weeks after the replaster, and added acid in regular doses to bring the TA down while keeping the pH in range.

So, now today, my results are (using trichlor pucks to add CYA over time until I get it to 30-ish):

FC = 5.0
CC = 0.0
CYA = 20
pH = 7.7
TA = 140
CH = 190

No salts no borates. With these plugged into the CSI formula, I get a CSI of near 0. Or -0.03 to be exact. Just where I want it to be.

But my question is: as my TA drops further to the 70-90 range, my CSI will go down into negative territory. To balance that, should I add more calcium hardness? Or should I allow my pH to rise to 7.8-7.9? I'm afraid to add more calcium hardness because of potential scaling. What would you pool gurus do?

 

[duraleigh]

and added acid in regular doses to bring the TA down while keeping the pH in range.

Did you follow the "lowering TA" article in Pool School?

I would leave my TA alone unless you have a valid reason for moving it. If you must move it, do so according to the article in Pool School....not just muriatic.

If you keep your parameters within the guidelines we suggest, there is no need to calculate CSI

 

[JasonLion]

Long term you will want to lower TA and raise CH, unless you have very high TA fill water. However there isn't any rush to do that right away.

You actually want CSI a little negative (say -0.2 or -0.3).

 

[yardoasis]

I'm not trying to reach a particular TA target, I just know that my fill water had a TA of 200 and when adding regular acid doses to keep pH below 8, the TA naturally comes down. So I started at 200, and now it's at 140. In order to maintain pH below 8, I add a couple cups of acid every other day, so the TA will come down further.

Jason, I did a bicarb startup so the CSI was positive for the first few weeks, and now I'm bringing it down to 0. If I want to keep it at -0.2 or so, then I can leave the CH alone and allow the TA to come down over time as I maintain pH of 7.6 to 7.8 (with new plaster). I may decide to add borates once the TA comes down to 70 or so.

 

[yardoasis]

Update:

It's been over 2 months since the replaster. Plaster looks good as new.

I have just switched back to bleach when my CYA reached 40, and that marks the end of my bicarb startup. My test results are:

FC: 4.5 (added bleach to bring it up to 6.0)
CC: 0.0
pH: 7.8
TA: 90 (had been slowly and steadily decreasing during the start up with the acid doses, and should settle to a consistent value soon)
CH: 210
CYA: 40

CSI: -0.17 (has been between 0.0 and -0.3 the past few weeks, largely controlled by temperature and pH)

No borates yet, but I may consider adding borates when the weather warms up (CSI increases with temperature) and when TA reaches about 70 or so.

I'm finding that with the cold and cloudy weather and pool water temp ~40-50 degrees, my daily FC loss is only about 0.5 ppm. So that should save me some money throughout the winter and early spring.

My plaster problem has officially been resolved and closed.