Hello and thanks for any help. My home was built in 71, Florida block home. Purchased about 10 years ago. For the past 6 months I have been having a drain fly issue in one bathroom bathtub, looked on-line, kept reading that the foaming drain killer would get rid of them, tried this, at first I believe it helped, they went away for a few days but came back. Ive prob. dumped a dozen down the drain now, I assumed that maybe the winter cold might get rid of them, didnt have much of a winter here this year, they did seem to disappear but with warmer weather they are now back. Rented a drill/wand cleaner deal, ( this A.M ) ran it down the line, never had much of a draining issue, dont believe there is or was any major clog. Dont think this helped. Took the cover off the septic tank which is maybe 15-20 feet away from this bathtub drain just outside the house, thousands of drain flies, they are everywhere in the tank, I believe they are just coming back up the pipe into the house and this is the closest exiting drain for them. What can I do to get rid of these things?