Ice Box
Jim, I have a Catalina 27, and get backflow into the icebox anytime that I leave the attached seacock open. My boat has been retrofitted with valves, but I think the config is still the same as the orginal. There are two valves on the sink/icebox assembly, one controlling flow to sink, one into the icebox. The valve going to the sink only shuts off flow out of the sink, through the hull, and into the sea. The foot pump on a 27 only moves water from the water tank into the sink basin. From there, it is at the mercy of gravity and the position of the seacock going back through the hull(and sometimes the temperature(density) of that water as well. Both seacocks/valves should then be in the closed position each time you leave port, and remain that way until you want to drain either the sink or the icebox. Hope this helps!Rob