An easier and less messy way to drain any water or debris from the tank is to orient the coach (park on a hill or with boards or with jacks if equipped) such that the area under the fill is the LOW POINT. Let it sit for at least an hour. Water and/or dirt, being heavier than diesel will migrate to the low point.
Then wire ties a piece of hose to a straightened coat hanger so that you can position the bottom of the hose in the deepest part of the tank. Then lower the other end of the hose to ground level and siphon off any water or debris into a glass container.
Brett Wolfe 1993 U240
In our coach removing the fuel tank, the drain plug will allow diesel to splash/spill on top of the bay floor, under the tank where it cannot be cleaned. It will also flow into the floor inner structure, and destroy the Styrofoam. And diesel smell never seems to go away. There is NO WAY of unscrewing that bolt and not getting fuel all over you.
We use the recently mentioned inexpensive $10 ‘drill pump’ with a couple of lengths of short garden hose attached to both ends of the pump. On the suction side hose, we insert a bent copper pipe that will reach to the bottom of the fuel tank.
Occasionally, we pump out a gallon of diesel from the bottom into a large glass jar. We let the jar sit still for several days so any water and biocides will find their level, water on the bottom, fuel on top with any bacteria in between.
We look for different layers near the bottom of the glass jar, but over the years have only seen clear diesel.
We carry several quarts of Power Service Bio Kleen & Diesel 911 and three spare fuel filters, just in case we get some bad fuel with water.
For the last 12 years, we also add “Power Service Diesel Kleen + Cetane Boost” (Walmart) to every fuel fill-up. We, as a rule, do not believe in any additives as they seem to be more marketing than anything else, but somehow Diesel Kleen made to our exception list.by by Barry and Cindy 1997 U270 36′