Over the past few days, the pH in my pool has gone from 7.4 to 7.6 to 8 (yesterday). This morning I measured the pH and got a reading of 8. Both the PoolMath and the treatment table of the Taylor test kit said to add 18oz of 20 baume Muriatic acid to the pool, which I did. This should have put the pH at 7.4-7.5. At 4pm I tested the pH again and got a reading of 7.8. I tested again at 10pm and got a reading of 8. I ran the test twice with different water samples just to make sure there was no mistake. The acid demand test is again calling for 18 oz. I don't understand why the acid I added earlier didn't correct the problem.
Also, I tested TA at 70 and have a CYA level of 35 and currently the FC is at 1. Page 14 of the taylor test kit directions say that I need to correct for cyanuric acid to measure total alkalinity using a formula ALKc = ALKta - (CYA * .33) which would result in a corrected TA of 58, which is too low according to the website recommendation of 70-90. Should I go by the corrected measurement or the original measurement?