Tannins in Pool Water?

[PoolDoc]

"2" is not a possible reading for CYA. Did you mean "20"? What kit are you using? Anyhow, with ZERO algae, your FC should be 5% of your CYA.

Are you using 31% muriatic from Lowes, etc? If not, you should be. I don't understand how you have pH/TA/CH that high without cloudiness. But if 1 quart at a time is not producing a change, go to 1/2 gallon per dose.

UNLESS . . . you are using diluted acid. If so, try 1 quart when you get full strength acid. And, READ the "Using Muriatic Acid" page linked in my signature.