Any help would be greatly appreciated.
Our pool was finished last Memorial Day - gunite pool with arctic white Hydrazzo plaster. Around September of last year we began seeing stains around the main drains. Then they started appearing on the steps. Then they started appearing everywhere. The stains are a grayish to black color and have basically streaked and mottled the entire pool.
Our pH has always been 7.4-7.6. Chlorine has always been between 2 and 3ppm.
I had the water tested at 2 local stores (Leslie's and Warehouse) in efforts to determine what the stains are. Other than phosphates being high, all other metrics were within expected ranges. No metals. I have tried the vitamin C tablet tests, lemons, limes, Jack's stain ID kits, pumice stones - NOTHING does anything to the stains. Our builder couldn't tell us what they are but did determine that direct application of muriatic acid will lighten and eventually remove the stain. The issue is that they come right back within a couple of weeks.
At this point the recommendation was made to drain the pool and have it acid washed. This is hard for us to accept when the pool is <1 year old and has been kept in the 'correct' levels as far as chemistry is concerned. I want to know what the stains are and what is causing them. If acid washing is the solution, that's fine - but I want to know that the stains will not come back.
Again, advice is greatly appreciated. I am hoping someone relates to the pictures and can explain what is going on.