Here are some pics of a neighbor's pool. It is a gunite, 15000 gal play pool with some major discoloration. It is a chlorine pool where the owner says he just shocks and adds tablets when the pool store tells him that it needs it. It is between 15 and 18 years old. The brown is mostly on the walls and steps - not so much on the bottom.
Any ideas of where to start? It looks as if the gunite has worn down in places, the discoloration (brown areas) are smooth, the blue areas are sandy (like gunite) as far as I can feel. I took a sample and this is what I found:
CYA - I'LL GET THIS AFTERNOON - IT WAS DARK AND RAINING (NO SUN)