Add bleach to main tank. Run water to every facet until you smell bleach. Also run it through the water heater. Let sit, how long depends on concentration of bleach. Dump fresh water tank and water heater. Refill and run the system until no more bleach smell from any facet. Special procedures may be needed for ice maker, washers, etc.
Some people sanitize their system every few weeks, some never do it for years.
Fred & Denise (RVM157) New Mexico
2007 Excel Classic 30RSO & Coach House 272XL E450
2007 RAM 3500, Diesel, 6Spd Auto, SWD, 4x4, CC & LB