They come together at an ABS wye, then from there, there is a reducer, and it is bronze barbed fittings to hose to bronze barbed NPT to bronze seacock. Bronze, not brass. (I can't believe the guy at the marine store was showing me brass... sigh) So everything below the water line is bronze and thickwall (reinforced) double clamped hose, so it has "give" where the plumbing meets the hull. I still have to make sure I can fit the ABS in the room under the sink... (do you hear that voice of failed projects... what was his name, "gobi" out there waiting... )

Defender also has stainless 304 drain baskets... vice the plumbing shop "magnetic" stainless. I am going to trade up for those, no point in having to replace these drain baskets anytime soon.

The head is already thickwall (reinforced) double clamp hose connected to all the appropriate fixtures. It is the galley sink that is giving me grief right now

The problem with plumbing... any plumbing, is all the various sizes that are not so easily "adapted;" at least with high grade "marine" parts. Oh and chrome plated plastic... really, anywhere? That chrome rubs off in about 10 cleanings, that stuff should just not exist at all, anywhere. I hate that so much of home plumbing is now that crappy chrome plated plastic.

If I could find a wye, that is barbed 3/4 and bronze, I would be all set with all reinforced hose connections to either of the sink drains. I can't seem to find it in either bronze or marlon, so I have to bring everything together in ABS at 1 1/2, then reduce to 3/4 for the final connections.

The interesting thing is that Groco has this huge manifold (below) that brings together 5 connections... but no simple barbed wye "Y" Go figure.