I have a quartzon pool, its 2 and half years old and within 6 months these blotchy patches began to appear at the top of the pool walls and continued to get worse overtime running down the walls to the bottom of the pool. I have been in contact with manufacturer of the surface 'Quartzon' as soon as I saw it appear, and they continued to tell me it was just calcium build up.
To cut a long story short. I finally convinced them 6 months ago it was not calcium and had them come out to inspect. After debating and having one technical person from another to view it, they still have no idea what it is or what is causing it. They have decided to semi-drain my pool and acid wash a certain section of the wall to see if it fixes the problem. If it works, they will drain the entire pool and acid wash the entire surface.
Does anyone out there know what this is, or had this problem? If so I would very much appreciate your help and advise on this. I have attached images of the surface of the pool.
I am very particular with my pool and have always kept the chemicals balanced and strictly followed the instructions to brush pool walls. Everyone that comes to see the pool comments on how clean it is and how great it looks until they look harder at the surface and see the problem.
Looking forward to seeing what you say.