What's supposed to be on the bottom of the fuel filter assembly? On mine, something seems broken off and there's a small constant drip. Is it a plug, a valve, and when is it used? Is it used for draining water, or is it to drain fuel when changing the filter? I don't want to take the unit apart until I have everything I need lined up to put it back together again. I do have a new filter cartridge ready. If you know the specs on the bottom thing (e.g., thread size), maybe I can get a generic one. Thanks fo rany advice.