A great little trick to flush your fresh water system with simple bleach... Trying to add bleach directly to the tank is a PITA.
Assuming you have fairly new/recent - clean white freshwater hose, place one end into the water fill of your RV. The amount of beach required varies with the size of your fresh water tank but usually, about 1 cup per 20 gallons works well for maintenance purposes. Fill your tank half full then pour the bleach into the end of the hose and connect the hose to your fresh water supply and turn it on. The bleach will be delivered directly to your tank. Drive around for a few minutes allowing the water/bleach mixture to circulate and don't forget to run all of you fresh water outlets {sinks, showers etc.} which will carry the bleach water mix through all of your water lines.
Let everything sit overnight and then drain your entire fresh water system. Refill, drive around a little and drain at least once more and you should have nice clean, drinkable, dare I say tasty, fresh water on demand. For us, this is just routine, yearly maintenance but it keeps everything from coffee to cocktails {ice} tasting just fine.
This technique comes in handy if you ever take on a batch of bad water {it happens more than you might think}. To prevent this never allow water into your tank that has not passed through an external filter {they are cheap and easy to use}.
To own an RV and not be willing to drink the water is like having a coach with a bathroom you won't use or a bed you won't sleep in. You might as well google Holiday Inn and get on down the road... :S
As always... Opinions and YMMV.
:B