For managing TA, it seems I have failed to keep my TA at 70, hence lots of acid required. My fill water has high 150-160(?) TA which doesnt help. I need to figure out how to lower and keep them low, been having to add a couple gallons MA per week to barely keep TA at 120 with the SWG on.
For an outdoor pool (i.e., one with CYA), the pH isn't critical for sanitation but for saturation. Most scientific discussions on that topic take into account the saturation index is comprised of a half-dozen components, where TA is only one of them, albeit an important one (pH, Temperature, CH, TDS, CYA, etc. being some of the others offhand).
I bring that up because what you would decide to do with your TA isn't done in a vacuum, but in light of what those other half dozen levels are, where, for example, the CH matters almost as greatly as does the TA in terms of where the saturation is on the etching/balance/scale meter (which itself fluctuates greatly with temperature).
Assuming a lot that wasn't said about those other half dozen components of the saturation balance, I've seen recommendations to manage the TA and CH in tandem at something like a 3:1 and even 4:1 ratio (the ratio not being important but the saturation balance being what you're trying to maintain).
Example: If your TA is 150 and you want to drop it by 20, do so with acid and then soon thereafter raise the CH by three or four times the TA drop (that is, by 60ppm to 80ppm). Keep doing this until you have the TA where you want it (while maintaining the original TA/CH ratio).
The theory here is that process of lowering the TA (in order to better control the pH ceiling) along with the CH (mostly to offset saturation balance) maintains the etch/balance/scale saturation ratios as they were at the start.
Also notice that you want to always work in small increments, so using the same method, if your TA is 150 ppm and you want to drop it by 100 ppm, you STILL do it in increments of 20 ppm (raising the CH in increments of 3 or 4 times that) until you arrive at your goal of TA 50ppm (and concurrently your CH would have risen by 3 or 4 times what the TA fell by).
Of course, this assumed a lot of unstated levels, so treat it as a general process that you will need to customize per your own pool's saturation index (which is a function of more than just TA and CH of course).
it’s more like about 4 gallons of 10% a week in a 20k gal pool.
Thanks. I put in about a gallon of HASA (12.5%) a week but I was wondering what others use. If it's four times that for most outdoor pools, then that multiplies the forever cost by four times more.
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