Procedure to Sanatize a Fresh Water Tank

Turn the water heater off and let the water cool.
Dilute 1/4 cup of household bleach for each 15 gallons of tank capacity in a gallon of water.
Add the chlorine solution to the water tank. Never pour straight bleach into the RV water tank.
One faucet at a time, let the chlorinated water run through them for one or two minutes. You should be able to smell the chlorine. (Make sure you are using the water pump and not an external water supply.)
Top off the water tank and let stand for at least three hours over night is better.
Completely drain the system by flushing the faucets for several minutes each. Open all plumbing drains (if any) and the hot water tank drain plug and drain until the tank is empty.
Close all valves and faucets and drain plugs.
Fill water tank with fresh water.
Flush each faucet for several minutes each repeating until the tank is again empty. (Make sure you are using the water pump and not an external water supply.)
Fill the tank again. The water should now be safe to drink but if the chlorine odor is too strong you can repeat the fresh water flush.