I have been battling fungus gnats (not drain flies) in my 44 year old slab house (on Septic Tank) on and off since we moved in back in 2001. The gnats are bad spring summer and fall. In winter they go to Miami. I have since put a new roof on so it is not roof/moisture related. I have no plants or other organic material in the house. I have had a plumbing company smoke my drain pipes but all they did was blow the water out of the toilet bowl on one of my toilets. The gnats must be a result of a moisture issue somewhere in the house. I want to start peeking in my walls to see if I can find a scorch mark (moisture). I'm looking at $600-$1500 range and want to make sure it is self lighted and prefer a smaller head such as 9mm. Waterproof head a plus. Recommendations?