From previous post:
I just bought a new filter by calling the 800 number on the filter. They said I could save money on both the filter and the shipping by logging onto www.thehotdeal.com
and ordering there. Click on the Watershed Filtration icon. Apparently this website represents several companies including Manufacturer's Warehouse Supply, Inc. that actually sells the filters for Alpine Coaches. I ordered two and both arrived three days later. Fit perfect and include the brass connectors that make the switchout a breeze. (I was very happily surprised!)
The mention of reversing the filter is to clean it. Simply install it reversed, run it awhile to flush out the debris into the sink and then reinstall correctly. This will clean out the particles that accumulate on the first screen.
To further confuse you... By design, reversing it will first flush out any debris collected on the previously first screen, but since the design is the same in reverse, by leaving it installed backwards, it now uses the screen originally at the end of the run. The center section is carbon and not dependent on direction.
However, they recommend replacing every six months. I replace mine annually.