Unlike some of the other types of flies and insects that are attracted to food particles and trash, drain flies are attracted to moisture and shallow water. If you have water stagnant around the house, drain flies are likely going to hover over them and cause an infestation in the long run. But that doesn’t mean that the drain flies don’t infest over food crumbs and organic waste. You need to be mindful of every last bit of trigger around your home that could be causing an infestation and get rid of the same for good.  Some incidents have even shown that drain flies can infest in cleaner areas too. So, even if you tend to have a clean workshop or basement, the chances are that you will need to check them every once in a while to rule out any possible infestation.