I have had a ongoing battle with a cultured marble bathroom sink overflow, which I have now figured out traps sludge, bacteria, mold, etc. at the bottom near the outlet holes in the metal drain tailpiece. I have poured bleach down the upper overflow opening in the sink for years. It helps only for a while and recently it has just gotten worse and worse.
I have now used baking soda & vinegar, foaming liquid plumber, Lysol, and rubbing alchol (not all at the same time), poured boiling water down the overflow, and flushed the overflow by filling the sink, and used qtips to pull crap out of the outlet ports as far as I can reach and obtained some relief.
I am convinced this odor is making me sick with constant sinus problems. After sealing off the top of the overflow and the drain the last 2 nights with duct tape, I woke up with no sinus issues twice, which does not happen often.
I don’t need the overflow as I never plug the drain anyway and I’m the only one using it. Is there anyway that I can permanently seal this off without replacing the sink, the plumbing, etc. or any other more permanent remedy anyone knows of? I am really not looking forward to having to spend time cleaning a sink constantly with qtips, etc.