How to Remove Water from Gasolineby Marie Mulrooney
It's difficult to determine how water gets into a vehicle's gas tank, but once it's there explanations are almost irrelevant. The most critical issue is how to remove the water from your vehicle's gas tank so that your vehicle will run well again. You can purchase commercial dry-fuel additives for this, or use the main ingredient in most of those additives, dry isopropanol alcohol, yourself.
Add dry isopropanol alcohol (IPA) to your fuel tank at a ratio of about 1/2 ounce of IPA per gallon of water-contaminated fuel.
Drive your car as usual. If you had only slight amounts of water in the fuel tank, the IPA will have soaked it up without significantly affecting combustion, and will burn away with the fuel.
Consider siphoning or pumping the fuel and water out of your gas tank if you continue to have problems--the IPA may not have absorbed all the water, and adding more IPA will disrupt the combustion process. If you do decide to siphon the fuel and water mixture out, siphon it into a clear container.
Let the contaminated gas sit until it separates. You'll be able to easily see the layer of clear water underneath the gasoline; it sank because it's heavier than gas.
Carefully pour as much gasoline off the top of the jug as you can without disturbing the layer of water. Use a funnel if necessary, and pour the gasoline into a gas can or other suitable container. As long as it's been kept clear from other contamination and solid debris, you should be able to re-use the gas now.