The bigger issue is that my PH is still at 7.8 this morning, after it being 7.8 yesterday afternoon. The pump was running all night so it is not a matter of poor mixing. My jug of acid that I used was old, probably a year old, but I put in a half gallon (yes, I know, too much . . . I got carried away). I can understand old muriatic acid losing its punch but not becoming completely useless. I have a 12,000 gallon pool and PoolCalulator.com tells me the pH should have come way down 7.0 or so, depending on the strength of the acid.
Could the acid have become completely useless sitting on the shelf in my shed? I live in Phoenix, AZ so it gets hot in the shed. It was Paddock Pools brand muriatic acid. I was shooting for a lower PH reading to bring my CSI into a more acceptable balance range. (And yes I know I need to drain about 75 percent of my water.)
I use a Taylor K-2006, and my current readings:
TC - 9.5
FC - 9.5
CC - 0.0
TA - 110
CH - 800
PH - 7.8
CYA - 150