I used to have a problem with moisture developing on my bathroom wall. According to the plumber, this was due to a leak in the waste-water pipe from the commode upstairs; the water would accumulate in the ceiling and eventually flow down the wall.
The plumber has sealed this leak and the wall has since been painted (it is not a plastic paint, it is more like whitewash). The wall itself has long since dried from the initial leak, and I have noticed no further problems with moisture accumulating on it. However, given that the wall had been exposed to waste-water for so long, I am concerned about whether or not the wall itself is still najis.
In particular, sometimes water from the shower will splash onto the wall, and then flow down (e.g. onto the knobs of my shower). I can't even be sure that my wudu and ghusl are still valid in such a situation.
I am looking for answers from a Sunni perspective: How should I consider my wall, and anything that comes in contact with it? Is it najis, or is it pak?