Thanks for the info, Ben.

I did as you suggested. I had just over two gallons of MA left. It took just under 4 boxes of washing soda (55 oz each I believe) until it stopped reacting with the diluted acid.

Btw, I visited 4 stores before finding one that had washing soda. ��

I have a few boxes left. I assume I can use this in the future in the pool to raise pH if needed? I usually have to raise pH at spring opening, and then it stays rock solid all season.