Drain flies can be exterminated with a simple metal drain pipe brush and any drain cleaner gel, according to the Get Rid of Flies guide. Once the breeding source is destroyed in this manner, the adult flies can then be dealt with using sprays or swatters.
Drain flies, also known as moth flies or sewer gnats, are small, light grey or tan colored flies associated with damp habitats. They feed on damp organic sources like the type of material that tends to build up in kitchen and bathroom drains. They can be removed by pouring warm water down the drain and cleaning it with a metal drain pipe brush. Next, pour a drain cleaner into the pipe, and after a few hours, pour plenty of water down the drain to remove any organic material trapped in the pipe.