I am planning to purchase the Jack's stain ID kit. But this is on my mind.
Have what I am fairly certain are copper stains (have used Copper based algaecides) and the staining is around the perimeter of the pool exactly where I pour my liquid chlorine.
So I tried crushing some Vitamin C tablets and dropping on a small area (12"x 12") of the staining. The spot immediately turned black (looked like copier toner) with the very edges of the spot a dark green. The area cleared overnight and the staining in that spot is a little lighter.
Wondering if this typical of how a metal stain would react to absorbic acid?