I do not have an infestation of them, but I do have drain fly's. I keep the shower/bath drains plugged and they still are present. There are no cracks in the foundation slab that go through its thickness. The fly's seem to congregate and die in the windows of my home. I cannot figure out where they are coming from.

Please help!!

You are talking about these:
http://www.cirrusimage.com/Flies/moth_fly_001.jpg

Right?

They can also survive in houseplants that stay damp, they can live in the soil at your bathtrap and climb up the shower pipe, they can survive and breed anywhere there is organic material and moisture

I have houseplants that I've brought in due to the cold. I (think) I eliminated them from the shower drain in a bathroom I'm upgrading/remodeling quite some time back (and hope they're not breeding in the soil at the bathtrap) and today found one that perhaps came out of a trash can in the kitchen. I've killed four maybe five in three days.

Advice?

Advice?

If the remodeling still has the bath trap exposed, lime the heck out of it. Changing the pH of the soil will make it less hospitable for insects and other decay organisms.

Houseplants can be treated with boric acid powder turned in to the top inch or two of soil. It won't hurt the plants, aerating the soil may help them, and you can eat boric acid straight it's so low in toxicity for mammals.

There are some larvae somewhere if you're seeing one a day or more. Good hunting.

Thank you