This year, I made the switch from tri/dichlor to liquid chlorine, in both my pool and spa, and have been rewarded with constant CYA levels, which is very pleasing. However, I have been having to deal with a new problem, especially in my spa: pH drifting upward. I have a 355 gal spa, and every time I use the jets, the aeration causes my pH to go up by at least 0.5. Every time I test it, it's up in the 7.9 - 8.0 range or higher. I put in acid to lower it back down to 7.3 or 7.4, but another use with the jets and it's too high again. I try to keep TA around 130 - 150, which is supposed to buffer against the pH swings, but it doesn't seem to be doing much good. And then, every time I lower pH with acid, I'm also lowering TA, and so I have to add baking soda to counteract that. Before, all I had to use was dichlor, which also lowered pH, counteracting the aeration somewhat, and only occasionally had to add acid -- and hardly ever added baking soda. (CH and CYA in my spa are 130 and 35, respectively, FYI.) Things were more convenient before.
Similarly, in the pool, though not as bad. Since the switch, which coincided with a drain and refill, I've been having to add about 3-4 gal of muriatic acid (14.5%) a month, with the requisite baking soda to keep TA constant. (I've been keeping CYA in the pool around 65 -- we have very sunny summers.)
Does this sound normal? Is it the price to pay to keep CYA constant?