I've also been using an external filter, the cheapest sold by Camping World (about $20 each, supposed to last a year but they clog up faster depending on local water supply). I've been told you should filter any water coming into the coach to prevent rocks, sand, etc from causing problems in the plumbing, even if you further filter it inside for taste purposes. I use a Brita pitcher for coffee, tea, etc.
I recently met Bill & Linda Grover who are full-time RVers and Escapees. Bill developed a rechargeable activated carbon water filter. It can be used over and over, and it does a much better job than any of the throw-away filters. It can be back washed every couple of weeks to get rid of the things filtered out, and it doesn't limit the flow of water. It removes chlorine and most of the odor and bad taste, along with grit, sand and other impurities. It costs $32 for the filter and a short hose to connect to the water source. An extra filter bag and carbon refill cost another $8. It will be a few years before I'll need the refill, but I got it just for insurance.
I'm not getting anything out of recommending this filter other than satisfaction from knowing I might save some fellow RVers from buying multiple filters that will just clog up and need replacement before the expected time. If you're interested, contact Bill at
mexycanamigos@aol.com or 928-341-8163. The filter is called "O-So-Clear." Bill's home base is in Yuma, but I met him in Las Vegas, so I don't know where you'll find him currently. Tell him I sent you!
Hugs,
Sharon