I wrote this article several years ago for a web site I owned about bus conversions, but it applies to all RVs.
Every RVer should have two filters for their fresh water system. One for removing sediment (but not chlorine) prior to water entering the RV and one to remove chemicals after it leaves the tank (before you use it).
I suggest you add a 10 to 15-micron dirt and sediment pre-filter right at the city water hookup. I use the string type readily available at Home Depot or Lowe's. They work fine and are priced fairly. Remember to change it once in a while. I change my pre-filter at the city hookup whenever it looks dirty, usually every couple of weeks. Use a see-through plastic canister whole-house type so you'll know when it's time. A whole-house type canister will have 1? pipe openings. Using a pre-filter at the city water connection will make your in-coach filter last a long time, maybe 6 months or so.
Use a carbon filter in a coach-mounted canister to filter what comes OUT of the tank. Carbon filtration is used to remove bacteria and the like, it also removes the chlorine from city water. If you use a carbon filter when filling your tank you are taking the chlorine out of the water and the tank interior will grow stuff if left sitting.
If the water in the tank is going to sit a few days or more, fill the tank through the gravity feed and add some chlorine. Remove your carbon filter in the coach and run water through all the faucets until you can smell the chlorine. Personally, I always park my RV with a full tank of chlorinated water. (The less stagnant air in the tank the less opportunity for mold to grow.)
Suggestion: Keep your fresh water tank fresh. Never use the city water supply connection on your RV. Fill your tank and draw water from the tank with the pump. In other words run all the water you use in your coach THROUGH the TANK. That way water cannot stagnate in your fresh water tank and as a side benefit, you'll never have a broken pipe flood from too much pressure.