6 Answers

Lots of good info here J...http://www.doyourownpestcontrol.com/drainflies.htm

Are they perhaps in the downpipe from the gutering to the drain from around the house m/c/m,??

Do you have a garbage disposal?  They live on the debris which remains after you dispose of food there.  There is a great cleaner, it foams and deodorizes the unit.  We get it at the dollar store here, it is actually about $3.  Works great, we use it as needed, but once a week is recommended. 

Dunno. We have the same problem off and on. take a small jar, add some vinegar and a drop of liquid soap, cover with plastic wrap and poke holes in the wrap. The vinegar draws the flies, soap makes ‘em stick. Kill the little ba*****s………….

Don't use bleach if you have a septic tank, as it kills the good bugs that break down the contents.

By septic tank, I mean the reservoir for waste water, not our American friends.

Are you talking about gnats. Much smaller than a common fly.