My dishwasher isn't draining, so I removed bottom spray arm, cover and screen. I am down to a black round part that is in a depressed area and there is a small screw in the middle. The black round part has a 25mm fitting and the screw is in the middle of that. I have tried holding the black part with a wrench and turning the screw. Is this screw right handed or left handed? I cannot get it to turn so that I can get into the impeller that I hope is clogged not broken. The DW was in the home when I moved in 5 years ago and I really don't want to spend alot on a DW that I figure is 10+ years old.