pH keeps creeping up

[chem geek]

Charles,

1) Any particular reason to fight my pH lower than the 8.0 that's been working well?

The main issue with running at the higher pH is that it is further away from the pH of human tears which runs closer to 7.5. Chlorine is less effective at the higher pH, though not by as much as the traditional graphs show because of the disinfecting chlorine buffering effect of CYA.

2) Recommended borate level?

50 ppm Borates will be a decent buffer (the numbers in my previous post used this amount) and will act as an algaecide. The "ppm" is technically measuring Boron. The test strips (AquaCheck) will accurately measure this level.

3) Recommended TA and Cal level for best protection of my plaster?

The water parameters of your pool -- especially pH, TA (and CYA), CH indicate that your water is over-saturated with calcium carbonate. That is, it will tend to scale or become cloudy. The index is at +0.6 and usually people start to see problems around +0.7 to +1.0 so you are on the edge for that.

The easiest thing to do is to lower your TA to 70 ppm and use a pH target of 7.7. That will give you about the same rate of carbon dioxide outgassing as your current TA 130 with pH 8.0. However, this should improve your acid usage since you add acid to have the pH go down to 7.4-7.6 where it outgasses more to rise to 8.0. At the new targets, it should take a lot less acid to keep the pH near 7.7 and you could swing between 7.6 and 7.8, for example.

4) Should I go higher with the CYA? (and hold the FC correspondingly higher?)

That is up to you, but if you increase your CYA, then have your TA level higher accordingly. The CYA contributes one-third of its ppm level to the TA value. So if you go to 70 ppm CYA, then make your TA target 80 instead of 70 (when you add more CYA, the TA will go up so you shouldn't need to change it -- just note the higher target TA).

Richard