Thanks, Evan. That's a fine detail I didn't know.

The moral is you MUST process what pool store guys say and do a reality check on them.
How can a pH of 7.8 be low?
Saying that the T/A of 75 would could acidity to eat your copper means the PSG (Pool Store Guy/Gal) doesn't know what T/A is.

Hey! I like that! Don't get Poolstored by a PSG !