Here at Strikeforce we use a professional grade foaming drain cleaner that not only keeps your drains flowing freely but eats the gunk and scum that collects on the sides which is the perfect breeding ground for small flies such as moth flies and fruit flies. Sanitation is the key to preventing these types of pest and the best place to start is with a Strikeforce Drain Defense Program.
Moth Fly Fruit Fly
1.^ By John Tann from Sydney, Australia (Drosophila immigrans), CC BY 2.0, via Wikimedia Commons
2.^ By Sanjay Acharya (Own work), CC BY-SA 3.0 or GFDL , via Wikimedia Commons
3.^ By André Karwath aka (Own work), CC BY-SA 2.5, via Wikimedia Commons