Valve in the head sink drain thru hull..
is a well worthwhile investment. If the thru hull fitting is a palstic one, I would replace it with a bronze one. I know of one Hunter 30 that sunk while at its slip during winter storage. During a heavy snow fall the weight of the snow on the deck raised the water line such that the plastic thru hull for the sink drain was below the water line and as the water froze around the waterline, the fitting burst,allowing the boat to fill with sea water as the ice thawed. But as regards to the galley sink drain, I would tend to leave it where it is, as long as it has a good valve to turn it off when the boat is not in use. You would need to place the new thru hull high enuf above the waterline to prevent any possibility of flooding the boat that it may no drain very well. Not to mention the stain that you may end up with as the "grey" water would run along the hull side.
