Keep Drains Clean & Covered
Use drain cleaner gel once a week to keep organic matter from gathering in drains. Drain gel should be applied when the drain will not be used for several hours, usually at bedtime.Drains that are seldom used can be covered with a drain stopper or a flat rubber cover which can purchased at your local home improvement store to prevent drain flies from inhabiting the drain.
In homes or businesses where drain flies have been prevalent, you should use an insect growth regulator that is labeled for drain flies. Insect growth regulators stop immature drain flies from being able to form into breeding adults. Insect growth regulators come in concentrated liquids and ready to use aerosols and can usually be applied into catch basins and around susceptible drains.