Finally, after over 6 months, the 3 spots in my pool where rebar was rusting through were correctly fixed. The pool was drained half way to get to the lowest spot. The other 2 spots were behind the water line tile.
Anyway, the grinding and cutting disks made quite a mess cutting back rebar. When I came home, there was a mess on the bottom of the pool. Large brown areas along the bottom wall edge starting from where the repairs were done and extending several feet. I vacuumed, but it did not all come out. Its stained the plaster brown. I dropped the pH and brushed and its 90% gone. But no matter how much I brush, I can't get the final little bit out. If I pour muratic acid right on a spot using a pipe, it clears that spot, but I don't want to add any more acid at this point. And I'd rather not pour in some stain remover from the pool store until I know what it will do to the pool. Any ideas?