Dry drains or j-traps either under a sink or below a basement floor can result in an infestation of sewer flies. Also known as drain or moth flies, the sewer fly is found in many drains, bathroom pipes and other moist plumbing areas where organic material collects. Sewer flies are small flies that resemble a moth. In small numbers, they can be helpful in breaking down material that blocks drain pipes. However, sewer fly infestations grow rapidly and serious infestations can create health hazards. One reason for having an infestation is a dry drain. Make sure all drains in your home are “filled” with water. Run water down every drain at least twice each month. Don’t forget basement floor drains, unused basement bathrooms and showers. This will stop most infestations from traveling from the sewer into your home.