[Richard]

Ok, I am in the minority here. Don't put any additives in the tank to absorb the water. Why? The additive is methanol. Methanol is a polar solvent meaning one end of the molecule will attach to hydrocarbons and one end will attach to water. Sounds good right. Except methanol is only soluble to a very small percentage in diesel or gasoline. Put in too much(and who would do that? thinking more is better) and now you have methanol/water mixture sitting at the bottom of your tank. That mixture won't pass through the filter any better than water.

If you think I'm full of it. Try this. Put some diesel in a clear jar. Add a ounce of water. Let it sit. You can see the water on the bottom. Now add 1/2 ounce or so of your preferred water absorber. Tell me what you see on the bottom of the jar.

Do what Jimmy said. Let the coach sit, preferably with the tank drain a little downhill. Drain a little fuel. Carry a couple of filters and some unopened ATF for priming the filter. Keep changing them until it clears up.

Do you a Racor filter? it should be trapping water, you can drain the filter to release the water.

I'm not anti additive. But additives won't solve a water contamination problem. They are great for lubricity, cetane boosting, and killing algae.

My grandad told me water and oil don't mix, my chemical engineering professors told me why.