sump pump

Am I correct that water from the galley and head sinks drain directly to the ocean via a throughfitting under the waterline? What about the shower? I have a sump pump panel switch, a sump pump switch under the lip of the head sink (no idea which position is on or off) and a jabsco 50psi model...

Has anyone installed an electric/automatic bilge pump or sump pump in their O'day 20 or similar? Is the bilge the correct place to expect water accumulation while underway? Are there other problem areas that also need pumps? Like in the transom area or the compartment under the cockpit hatch?