Your owner's manual will provide the sanitizing procedure with a bleach solution.

Alternately, from http://rvbasics.com/techtips/sanitizing-your-rv-fresh-water-system.html

"Start with a nearly full 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 to a gallon of water.

Add the chlorine/water solution to the water tank. (Never pour straight bleach into the RV fresh 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 RV fresh 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 the fresh water tank drain valve to speed up emptying the tank.and Open the hot water tank drain plug and drain until it 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.)"
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Use plain bleach, not scented.

Even with sanitizing the tank, we carry a water filter pitcher (Pur is good) for filtering drinking water from the fresh water tank or the campsite direct water line.