Quote Originally Posted by CarlD View Post
Since Evan sees firsthand F/G pools, I'd tend to take his advice first. In vinyl pools, I've seen t/a of 180 with no problems.
It applies to vinyl also. However, many AGPs don't have as much aeration from the returns and don't have water features compared to IG so there is less aeraton so they can get away with higher TA without major pH problems. However, lowering the TA will still contribute to pH stability. It's the basic chemistry involved!
As for muriatic acid, "slow" usually means a cup to a quart pour VERY slowly into the return stream. Better still is to pour it SLOWLY into a 5 gallon bucket of water, then pour THAT into the return stream--less chance of stray acid reaching the pool wall.

3 gallons????!!!??? Maybe if your pH was 9.5 in a 48,000 gallon pool and you wanted to make it into an acid wash! Pool stores! Feh!
This amount is what would be needed to lower the TA ,not for pH adjustment, BUT I wold not put it all in at once. I would follow the sticky on how to lower TA. This is around the total amount of acid that would be needed to do it.
Adding acid lowers TA, aeration brings the pH back up without causing the TA to go up again.
We believe in slow and gradual for all chemicals other than chlorine. If your pH is still in the 8's I'd add about 1/2 quart of muriatic acid and wait 12 hours, then check pH again. That's because you have 20K gallons and your pH is very high. Otherwise, I'd suggest half that--1 cup.
Until the TA is lowered the pH is going to be moving toward 8.0 fast and the acid consumption will be high.