As a start, tee the sink drain into the head sea water intake hose right at
the seacock. That way you can also feed fresh water to the head when
necessary, or lube oil, or antifreeze. Downside is you might have to put
sink stopper in to get good flow to the head.
Plumb the head discharge straight to the holding tank.

wrote in message
...
I'm about to begin the installation of plumbing components on a 30 ft
sailing cutter (new, "holeless" hull) with a basic complement of
fixtures which require through-hulls & seacocks:

Galley Sink Drain
Galley Salt Water Foot Pump
Engine Raw Water Intake
Head Vanity Sink Drain
Head Toilet Raw Water Intake
Head Overboard Discharge pre Holding Tank
Head Overboard Discharge post Holding Tank

My basic questions a

Which - if any - of these fixtures can share a common seacock, and
what are the standard or typical hose sizes for each of these
functions?

For example, can the galley sink drain and engine raw water intake be
'Y'd' off of the same seacock?
Likewise the toilet raw water intake and vanity sink drain?

Obviously, I'd like to minimize the number of holes I need to drill in
the hull, but don't want to violate any traditions...

Appreciate any thoughts.

Mike Worrall
Los Angeles