Ive never heard of drain flies, these flies look exactly the hatchlings we used to feed our frogs as kids. Anything I can run through the system to kill them or anything?If you see flies, what kind? Fruit flies? Drain flies? (Google and see.) If you have drain flies, make sure there are no dry traps, including floor drains. Even if a trap isn't dry, sometimes they can thrive on the gooey pipe walls just under the strainer (eg. shower drain). If so, remove the strainer and give it a scrubbing with an over-sized bottle brush ("dollar" stores are helpful for find those cheaply.)
I actually havent seen the militant bulldykes nextdoor for a while, haha.We had this happen one time, turns out a neighbor had passed away and nobody knew it for a month or two. We could not figure out why we had so many flies until we saw the fire department break her door down....
I've used this stuff in the past. Works great!Sometimes they are just tenacious and need spray. One of these will last you years probably. 1-2 shots per room a few times a day for a couple days and they will go away. Safe for use where food is prepared