Very FIRST thing I would do is to backflush that thing.
I like to get my air nozzle and garden hose both in the bottom hose and pack a wet rag around them.
Then give it a few seconds of water then hit the air.
(You probably want to be mindful of where the water that comes out the top hose is going to go because it's probably going to be nasty):D
This is free and at the very least will answer some questions for you.
