Recently, we had an influx of drain flies. They're annoying, little flies that tend to show up in bathrooms and kitchen. Apparently, they're some type of moth that reproduces at a ridiculous rate! I've read that they lay eggs in the "organic slime" that lives inside of our drains. The eggs hatch within 48 hours and they live for about 2-3 weeks (which rapidly mulitplies into nastiness!).
Well, several internet people recommend "killing" the organic slime, others said to pour bleach down the drain...I decided to go with soap and apple cider vinegar. I'm still not certain why you put the soap in...maybe it traps their bodies deeper down? It's heavier than the vinegar and sinks to the bottom. Day one, we had a ton of flies in there! Day two, not as many...but then, there weren't as many to catch. I think I'm going to go one more day to hopefully catch all the fellows that are hatching. This is a picture of day two. The black flecks are the flies. Yesterday (day 1), there was a pretty nasty black flecky ring around the outside.