Thanks Geoff. On my boat, the "icebox" that is next to the sink in the galley on the port side does not have any insulation, but it does have a drain, which can be pumped out like yours. But under the nav table to starboard there is a larger insulated icebox and this is the one I am trying to drain. Now that you mention it, it probably is connected to one of the foot pumps, too, or maybe the shower sump pump or something. I'll go look again.