pH is climbing too quickly...

[tempestuous]

I've had my pool for about 14 months. For the first year+, the pH would climb roughly 0.1 per day. So, I would add a little acid every couple/few days to keep it in check. From what I gather, this is normal for a newish plaster pool.

But for the past week or so, though, the pH has been climbing at twice that rate--about 0.2 per day. I have no idea why this is.

I'm measuring pH with a Taylor kit, and with a pH meter I bought a few weeks ago. The two of them always agree on the pH reading.

Everything is pretty much within spec:

FC: 9 ppm (a bit high, I know)
CC: 0 ppm
TA: 60 ppm
Calcium hardness: 350 ppm
CYA: 60 ppm
Salt: 3,000 ppm
Borates: 50 ppm

I added boric acid a month ago. It didn't do anything much to the pH at the time, nor for at least the 3 weeks after.

I haven't been doing anything different lately, other than adding ~6 ounces of Jack's Magic "The Magenta Stuff" every weekend for the past 3 weeks.

Nothing else unusual is going on, that I can tell. The water looks great. Nice and clear, no stains, etc. What could account for the doubling of the pH change rate?

Aaaaand... I just realized I've been running the pool's two arcs ("waterfalls"), which can increase pH. I can turn them off for awhile to see if that makes a difference. BUT... I've been running the arcs for several weeks! So, I am still confused!

 

[mikemass]

Are you running your T-Cell-9 longer than in the past? That causes pH rise too. Between the Salt cell and the Water Fall, those are the culprits.

Is this 0.2 rise per day like from 7.4 - 7.6? Or more like 7.8 - 8.0? Because pH bounce is not linear, it's algorithmic. Meaning the first 0.2 will occur quicker than the next 0.2 and so on. If you are stabilizing around 7.8, shoot to keep it there. You will drive yourself nuts if you are targeting to keep it in the low 7's.

 

[tempestuous]

I turned the T-Cell up a tiny bit a few days ago, but when I say "tiny" I really mean it. Like, less than 5%. It's on roughly 35% right now. (I run the pump 12 hours per day.)

Yes, exactly--from 7.4 to 7.6. I used to only check pH every couple days or so, and let it get up to ~7.8, then drop it down to ~7.4 or 7.5. Since getting the pH meter, I've been checking the pH more often, because it's so convenient. I guess I happened to notice the quick pH upcurve, and drew the wrong conclusion.

Thank you!!! Truly appreciate it.