• Add acid to lower your PH to between 7.0 and 7.2 (this also lowers TA)
• Aerate until PH rises to around 7.6 (the only way to raise PH without also raising TA)
• Repeat steps 1 and 2 until you reach the desired TA.
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You can lower PH with muriatic acid or dry acid/PH Reducer. You can get an estimate of the amount of acid to use with PoolMath. Keep in mind that the amount of acid required can vary from the estimate. If your test kit includes the acid demand test, you can use that to calculate the amount of acid required more precisely. Allow at least 30 minutes after adding acid, with the pump running, before testing the PH again.

Lowering TA can take some time, days or even weeks, depending on the amount of aeration you have and how far you need to lower your TA. Many smaller bubbles are better than a few large bubbles. Lowering the PH back to 7.0-7.2 more frequently will also speed up the process, though that can get tedious.