Shower vent moth fly drainage trap
We have had little black drainage flies in our bathroom for quite sometime, the master shower which is lined with ceramic tile. People come to clean once every 2 weeks. I have poured bleach and Draino down the drain, but the flies keep coming back. I plan to try this Orange Citrus Drain and Disposer Cleaner, bleach and recaulk the shower, but I have a feeling it won't get rid of the problem. Coiuld these be coming from the roof vent to the shower, could it be from the drain trap, or could it be a mold problem behind the tiles? Could the builders of the house be liable for this drain fly problem? At wits end! Any help would be appreciated?