Depends what's in the bottom of the fuel tank. I rigged a Goldenrod filter to the suction side of a 3/8" gear pump and a hose with a 1/2" copper tube wand that went down through the filler hole into the tank. I plumbed the pump discharge to the fuel tank outlet connection downstream of the shutoff valve. I ran it for 20 minutes, swishing the "vacuum wand" around all corners and the bottom of the tank. Worked great, got lotsa crap out (trapped in the Goldenrod) and the fuel is sparkling clean now. Don't even attempt to try this with a gasoline tank for obvious reasons, and don't be a Darwin candidate and use a drill pump either.