I own a 2-year old home and started noticing a brown stain accumulating at the bottom of a frequently used shower stall (3 ft. x 3 ft. plastic insert). Various commercial cleaners have been ineffective in removing these stains. I spent about 15 mins. scanning your archive, and was not able to locate a response from you on this issue.
Answer:
The answer is actually there in the archives. It has to do with mildew and mould that forms due to a lack of adequate ventilation. If it doesn't have to do with ventilation, it has to do with some form of impurity in the water and that is something you have to address locally.
