Low pH Brain Teaser

[DavidD]

Have to know the pH of the fill water to even hazard a guess.

+ 10.5k gallons of water @ pH 7.2 (fill water)

You wrote that initially the pH was > 6.8, but I suspect you meant < 6.8. Same with CYA that you wrote < 100 when I think you meant > 100. To measure 0 for TA, which means it turned red immediately, that implies a pH below 4.5 because that's the transition pH for the two indicators used in the TA test.

Yes Richard, you are correct in that I had my less than & Greater than signs all backwards. And yes, the TA test turned red immediately. Thanks for taking a stab at it. I made the same "assumption" that his pH was 4.5 or less based upon the pH not being affected by the initial 4 boxes of Borax AND the TA test turning Red immediately. I vaguely remembered you or someone else once making this statement in the past. Scary thing is that this doesn't seem to be that unusual. I know of at least one other pool that is probably in the same situation. I tried to offer a little advice but got "What I'm doing is working" so I backed off.
Is this 4.5pH dangerous to humans?

Dave

PS: I forgot to list it but the fill water has a TA of 80 ppm and the pH of 7.2 is actually a little higher based on the slightly darker shade.