John Its a good thing to break up what may have gotten into your tank from time to time any ole way. Go to your local dollar store and get some de-natured alcohol and pour the stuff into your tank. Or you can go to the local parts store and pay $ 2.79 or more. As for as testing for water....if you have a glass bowel filter that came on the older vehicles you would be able to see the water/glass line...if there is water. Rodger & Gabby 47 De Soto Custom w/glass bowel 63 Le Baron 66 Le Baron