After you have started to treat the drains with drain gel, it is time to get rid of the adult drain flies. You can do this with a pyrethrin space spray.
Products or tools needed:
Space spray refers to spraying an aerosol product directly into the air instead of directing the product onto a surface. Usually only pyrethrin aerosols are labeled for this use. A space spray is a good choice if you have a lot of drain flies inside and you need to get rid of the drain flies quickly. With this method, you will eliminate any drain flies that are out during the application but you will not leave behind an active residual. Following the product label instructions, apply the aerosol as a space spray. Most space sprays require you to vacate the room after the application and ventilate before re-entry. Please refer to the product label for re-entry requirements.
Left over pyrethrin spray can be used to spot treat or direct treat when new drain flies are found.