Good question. Not much room in the shallow bilge for installing or making a dedicated shower "sump". When we bought out boat the first thing I noticed about this was the switch panel on the bulkhead in the head compartment for (in theory) pumping out the shower water after it drained into the fancy teak grate.
Then I later pulled up the aft sole section when I wanted to split it into three sections, with a lift-out center panel. Nothing there for pumping out, and the hose and strum box for the remote Jabsco pump that was controlled by the switch inside the head was actually forward beneath the factory sole access panel behind the table.
What EY had done was install two separate bilge electric pumping systems, both $$$ Jabsco pumps. The other pump had its intake forward under the table under the lift-out panel under the table.
The good news that the boat has two electric pumping systems. Bad news was that this would allow hair and soap residue to move forward thru several bilge 'hat stringer' dividers. Ick.
None of this helps the problem found by the OP, tho.
I have imagined out a way to run a 3/4" hose under the sole to the drain hole in the head and glue it there. Then, so goes the theory, run that to a small pump under the aft sole. OR, run it to another remote mounted Jabsco pump and have yet one more exit thru hull in the transom.
Our solution has always been to visit a marina with coin-op showers every few days. Not the answer hoped for, unfortunately.
We used to carry a "solar shower" bag on deck for our former 26 footer, but it was a nuisance to deal with for showers in the cockpit.
Or.... just buy an Ericson 38 or E-35-3 !
(Just kidding, we love the Olson.)
