What is a home remedy to kill drain flies?

The most effective home remedy for drain flies is to disassemble the infected plumbing and scrub the pipes until they are free of any film. If the drain cannot be disassembled, home remedies are not effective and the best solution is to use an enzymatic cleaner.

Breeding sites can be identified by coating the inside of a cup with petroleum jelly or oil and inverting it over the drain in question. If the drain is a breeding site for drain flies, the adult flies will become trapped in the oil or petroleum jelly inside the cup and can be easily identified.