TA keeps creeping up even though I'm not adding anything for it

Started by Alan Pierce · · 2 replies
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#1
Been chasing this for about a month now. Total alkalinity keeps drifting up into the 130-140 range even though all I'm dosing is liquid chlorine, nothing with any buffering in it. I dose acid to bring pH down after, get TA back near 90 for a week, then it climbs again without me adding a thing.

Only variable I can think of is my waterfall feature runs a lot this time of year and that's a lot of splashing and aeration, which I know drives pH up, but I didn't think it moved TA on its own. Fill water from topping off evaporation is the other candidate, Marietta water's not wildly high in TA as far as I know but haven't tested it straight from the hose in a while.

Retesting fill water this week with the TF-100 to rule that out. Anyone dealt with a water feature actually pushing TA up over time, or is that just pH and I'm misreading my own numbers?

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#2
Had almost the exact same head scratcher with my sun shelf, water's shallow there and gets a lot of splash and off gassing on windy days, and I could watch pH climb without touching TA on my end at all. What clicked for me was realizing aeration only really moves pH, not TA, since you're just driving off CO2, the actual alkalinity number shouldn't budge from that mechanism alone. So if your TA is genuinely climbing and not just an artifact of testing right after a big pH swing, I'd bet on the fill water before the waterfall. My hose water actually came back higher TA than I expected when I finally tested it straight (Orlando muni supply), enough that a month of topping off for evaporation was quietly doing the work. Good call checking with the TF-100 instead of guessing, that'll settle it fast.
#3
Priya's right that aeration is a pH thing not a TA thing, that part's solid chemistry. What she didn't mention, and it's the piece that gets people every time out here, is how much evaporation actually happens with a running waterfall in this heat. You're not just topping off a little splash out, you're replacing a real chunk of the pool volume over a month, so whatever TA is in that fill water gets concentrated fast. Test the hose straight like you're planning, I bet Marietta's higher than you think.