Drain flies feed off sewer and organic matter. The eggs laid by the females hatch into drain worms in a matter of about two days. Here is a natural way to clean out your drains to get rid of their eggs and hatched drain worms…
½ cup baking soda
½ cup of salt
1 cup white vinegar
1 pot of boiling water
First, pour the baking soda and salt down your drain. Next, very slowly add the vinegar. The mixture bubbling and fizzing is normal. Allow it to sit overnight and then slowly pour the pot of boiling water down the drain the next morning. It is a good idea to make this a monthly routine to keep your drains clean and prevent the drain flies return.