pH won't go down

Early this season my pH was a little low so I added 1 4LB box of borax. It moved from about 7.0ish to 7.6. I was happy.

But continuing over the course of the summer and now into September I've been adding pH down because the pH has gone to 8.0! Over the course of a month or so I've added about 4x what the bottle said to add in attempt to reduce my pH from 8.0 to about 7.4-7.6, but it's stubbornly held around 7.9-8.0.

I've been using an acid salt called Sodium Bisulfate(93.x%) which I've purchased at Lowes and/or Home Depot.

Is it normal to have to add so many times more chemical to reduce the pH?
What other things can I try? I obviously want to be careful because I don't want to overshoot and go too low on pH.

I have a 24K gallon IG Vinyl pool and use liquid CL.
FC this morning is 8.0, usually closer to 4ish but I recently shocked.
CC = 0 which is typical
TA = 100
pH = 8.0
CYA = ~50

Thanks in advance for the help!

First, how are you testing your pH.
Some pH tests will read high if the chlorine level is above 5 ppm! Taylro pH tests are usually good for up to about 10-15 pppm.
Second, how are you testing the chlorine?
If you are using a DPD test (color comparator with red color blocks) instead of an FAS-DPD test (drop counting test with color change from pink to colorless) it is possible that your chlorine is higher than you think because of a partial bleachout of the DPD test.
Finally, if your pH is constantly high and/or rising fast and non of the above are true then lowering the TA will solve the problem. The main cause of pH rise in a pool is the outgassing of carbon dioxide and the higher the TA the faster it will gas off. Try dropping the TA down to about 70 ppm by following the proceduer in the forum.

Waterbear, thanks for the response.

I use a Taylor kit for testing my pH, TA, CYA etc and Taylor FAS-DPD kit for testing CL, so bleaching should not be an issue.

I'm below your 10-15 CL level so think my pH test should be reliable.

I added two more cups of the Sodium Bisulfate to my 24K gal pool about 4 hours ago and the pH has moved to about 7.6. Now I have to watch it because if history repeats itself it will inch back up.

If pH keeps inching up, I will follow your advice for lowering the TA to 70. Here I was real proud of myself for nailing the TA right in the middle of the recommended range at 100.

I can't get my ph to stay below 8.0 for more than a couple of days because of my high TA. My fill water has a TA of 170 & ph of 8.4 so it's a battle I can never "win" but I haven't really had any issues keeping my ph at 8 except that it does burn your eyes! :/

Quote:

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Originally Posted by myLABSpool

If pH keeps inching up, I will follow your advice for lowering the TA to 70. Here I was real proud of myself for nailing the TA right in the middle of the recommended range at 100.

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Actually, the recommended range for TA using unstabilized chlorine sources such as bleach (which are net pH neutral or close to it on use) is 80 to 100 ppm and below 80 is needed in cases where pH tends to rise fast (SWCG, fountains, negative edge pools for example). For stabilized chlorine, organic bromine, and MPS a higher TA of 100 to 120 is recommended since these are acidic and the higher TA will ofset their acidic effect by causing pH to rise.

Thanks for the info waterbear. I will lower my TA to try get my pH down as you suggest. It has crept up again to 8.0. I really want to get this right before I close --which is only a couple weeks away at most. :(