Fungus Gnats are controlled by locating the sources. They will live off of live plants and feed on fungi that is growing in the soil.
Inspect the potted plants and correct moisture.
Let the landscaped areas dry before watering again.
Look for water leaks, such as swelled wall coverings and water stains, fungus gnats may be breeding on fungi present.
Drain flies or fruit flies may be coming from your drains. Using clear tape, tape the drains (with little holes for an air flow) shut at night. Check the underside of the tape the next morning. Use Invade Bio Treatment in the drains to break down the organic debris in the drains.