You should always put a new hepa filter in any E and E2 series Rainbow vacuum, when it taken to a new home, or every two Years, or so, or if your Doughter makes it get funky smelling. :-) It will smell like the home that it was in, or how ever it smells, until you do.
You can also use fragrances, and deodorizer air freshener in your vacuum, which not only eliminates odors, it add fresh aromas to your air that you breath, in your home, also.
Replace the hepa filter first thing.
The water separator is the thing that spins in the center of the motor where your water basin attaches to it. It looks like a cone shaped fan looking thing. It should be cleaned after every use.
Use your Rainbow separator cleaning brush, or a tooth brush, if you do not have the Rainbow one. They are just like tooth brushes.
Never store your Rainbow canister on your water basin, with or without water in it. It can and will ruin your vacuum in dew time.
You can get manuals either here, http://www.rainbowsystem.com/
or here, http://www.rainvac.com
If you have any more questions let me know. I am a Rainbow seller, and a Rainbow expert also.