How can I get rid of black septic tank flies?

Where are the flies appearing ? Do you know where are they coming from ? First, you have to find the source of the problem, otherwise they will be coming back.

The flies may be a sign that the septic is not closed and sealed properly, is overflowing, or your ground is saturated with sewer. Check your sewer to see if it needs to be pumped out. Once the sewer is sealed, or pumped out, sewer flies will disappear.

As far as getting rid of them: it is going to be hard to chase flies with insect spray. You can hang fly-paper in the immediate area of infestation. However, unless you prevent sewer from being in the open, flies will be coming back.

Hope that helps

Milo

If the septic has overflowed into the lawn, they may not be sewer flies. Many species love the wet, organics rich soil. Nonetheless, fixing the septic has to be the first step, if only to deny them an attraction.

I have been infected twice.The only way I know to eliminate them is to starve them out. Cover ALL drains, install fly strips, and use bug spray where you see a swarm.
Drain flies have a life span of approximately one week. The secret is to starve them out before they can multiply. So cover EVERY drain even tub drains so they can not feed.
Good luck Tom