I have tiny flying knats in the apt. I have no plants in the apt. What are they, where are they coming from and what can I do to get rid of them.

I looked at your previous question and it may be pertinent. The gnats may very well be feeding or breeding in the moist wood from the toilet leak you asked about last month.

Other suspect areas would be any landscaping mulch just outside the windows or buildup inside the drains, particularly unused or seldom used drains such as a guest bathroom. Enzyme based drain cleaners can help with the latter, and turning the mulch to aerate it should help with the former.

What about old potatoes or onions in the cupboards. Are the gnats or fruit fly's?