My wife and I recently moved into a mobile home and are loving it... most everything is working fine, but I've noticed that the kitchen sink drains very slowly, and tends to get some back-up when the dishwasher is running. My first guess was the catch, so I took that off and looked, but it was totally clean... then I unscrewed the air filter thingy just past the catch in the drain pipes, and tried running water... it drained very quickly with no problems. When I went to a store and bought a new air vent and installed it, the sink went back to draining slowly. Am I missing something? Something else I should check? Or is that just the way things are gonna be for us? Any suggestions are welcome! Thanks!