Drain flies do not bite humans but may become a nuisance because of their tendency to present in large quantities. Sometimes it takes persistent effort to eradicate an infestation in the home. Drain flies thrive in stagnant and standing water. Common sources include slow or clogged drains, rarely used and unused toilets, refrigerator drain pans, and standing water created by leaking pipes. They typically enter buildings through basements, windows, and drains.
