[GringoPhil]

* Drain the fresh-water tank
* Add 1/4 cup bleach to every 10 gallons capacity as you refill the tank
* Use the on-board pump to run just enough water to each of the Cold lines -- until you smell the bleach
* Continuing with the pump - run the water enough to each of the Hot lines -- until you smell the bleach
* Now leave the system at rest (several hours or overnight) so the bleach can do its job

* Pump out the fresh-water tank (using all the faucets)
* [optional] some people like to add a small amount of baking soda to the fresh water tank at this point
* Refill the fresh-water tank (adding a few tablespoons of bleach if the new water is not chlorinated)
Done.

Also consider the quality of your fresh water hose -- it should be specifically labeled for 'drinking water'. Regular garden hoses introduce their own 'off' taste and should not be used.