Vacuum smells

Question

I have a 6 year old rainbow vacuum model E and it smells terrible everytime I use it. Probably because often times i don't remove the water basin after vacuuming and just let it sit. It's my own fault however now I don't know what to do to get rid of this terrible smell. I've water cleaned the hepa filter, not able to remove the separator s***w to clean. Can you give me some suggestions?