Main Drain Cover

[terpanther]

Hi,

I've got a very old inground concrete pool that I've done a lot of cosmetic work to. The pool was in horrible shape when we bought the house. Recently put new waterline tile in and think I'm finally ready to fill it up. During all this process, unfortunately, the drain wasn't covered and all sorts of dirt, tile pieces thinset and other mess have gone down in it. So I was going to take off the cover and clean it out (don't want all that mess in the lines). I can't get the dang cover off! It apparently has tamper-proof screws, but they are set deep in the grate and I can't tell what kind of heads are on them. They aren't metal, they are some sort of plastic. I'm not even sure if they are screws. I have a tamper-proof bit set and none of them seem to fit them. Should I drill them out and get new screws? Any ideas?

Thanks,

Tom