A drain fly is a gnat. It develops in moist areas like drains, pipes, and garbage bins. They are multiplying very fast by laying hundreds of eggs in moist places. Drain flies become more active in the evening, congregating around sinks and shower. On average their life span is one to three weeks.
Do you have drain flies? If so you could face major problems with drain in your house. Drain flies could be a very easy problem to fix. However it could just be top of an iceberg, meaning that you might have a very serious problem with drainage system.
Fortunately, most of the time drain flies are found in unattended bathrooms. Once water starts flowing, drain flies often disappear. Other effective way to deal with and prevent drain flies is to simply put bleach or drain gel into the drain every night for 2 weeks.
Unfortunately if bleach treatment doesn’t solve the problem, it could be a more serious problem. Many people try to call exterminators and pest control, they try to use bug bomb, but all these actions will only eliminate quantity of drain flies for short period of time. You will have to look deeper into the source of your problem. If bleach doesn’t help you should be calling trusted plumber with special video equipment what will usually reveal problem with your drain. Plumbers know much better about drain flies than exterminators and pest control. Problem could be anything from plugged drain to even broken pipe under concrete in the basement floor. Drain flies are not only annoying but also dangers. They dwell in filth, they could carry bacteria and other disease-causing organisms and transmit them to humans, making them a significant health concerns.
Expert Plumbing – Toronto Drain article.