Plaster staining questions

[Mesamav]

I had some stains in my pool and someone on here said to apply a dichlor puck to the stain so I tried it and it worked great on most of the stains.
There are a few stains that it didn't work on. Small, circular dark stains. I'm going to try vitamin C on those and see what happens.
Anyway, it's an older pool and the plaster has always had dark splotches on it in places but I thought those were permanent but when I removed the puck from those small, circular stains, I noticed that the puck cleaned the plaster very nicely. I also noticed that the surface is much smoother as well as cleaner where the puck had been sitting.
I can't use pucks to clean all the splotches because it would take a year so any ideas on what I can do????
I'll see if I can post some pictures tomorrow.

 

[chem geek]

The pucks are Trichlor, not Dichlor (which is always a granulated powder). Trichlor is acidic and a high chlorine level so works particularly well on bleaching out and oxidizing organic stains. It's not the best approach for metal stains. To handle organic stains overall in a pool, usually they will just fade over time from maintaining chlorine levels but will fade faster at shock levels. For metal stains, one can use ascorbic acid (Vitamin C) and do a whole-pool treatment as described in Metals in the Water and Metal Stains.