New apartment building recently completed construction June 9th. I moved in July 12th and now have drain flies (100% positive). There hasn't been any time for drain build up and I am on the 5th floor. How can this be?

It's easy to envisage eggs being laid in pipes sitting in the mud (All construction sites are muddy, even in arid climates) and not hatching until after completion. It's just as easy to imagine eggs being laid in the sewer tie-in process. Getting rid of them is definitely going to involve building ownership, as the infestation is likely widespread.

Today I saw tiny tiny little "things" crawling out of drain. I was under the impression that adults emerged from drain. Management claims no one else has a problem. Now what?

That raises the possibility of another species of fly. Have you tried any of the "scrubbing bubbles" type foaming ammonia cleansers?

The adults that I killed were 100% drain flies. I covered all drains for 24 hours and then opened one (bathroom sink) and that's when these teeny tiny brownish long things emerged. I poured drano gel down the drain and flushed with boiling water and repeated again last night. I have kept all drains sealed unless I need to use and then I reseal again. If I don't see any more adults will this be the end of them?

If I don't see any more adults will this be the end of them?

If you can keep them sealed for a month except when in use you stand a good chance of eliminating them. Something occurred to me in reviewing this: You might wish to verify that your neighbors aren't having problems with the neighbors instead of with the landlord.