I don't like the idea of adding water to my gas tank. I would flush the tank with gas while rocking the car sideways back and forth. With the valve removed the gas will quickly flow out and carry junk with it. Let the gas flow through a cloth to filter the junk and keep repeating until the gas flows without junk mixed in. Then install the little filter that fits the top of the valve and you should be good to go. You may get some fine junk for a while, but the sediment bowl will trap it for easy removal.