I am changing all thru-hulls and seacocks and replacing them with new ones from Groco. In the head, there was a 1 1/4" thru-hull for the head intake and a 1/2" thruhull for the sink drain.
The old 1 1/4" thru-hull flange had an unusual shape on the outside of the hull that was put in flush with the hull. When we took it off, the new thru-hull did not fit in. So we decided to close both holes with fiberglass mat and barrier coat. The 1/2" hole was right next to it and needed to be enlarged to 3/4" anyway (Groco's smallest size).
NOW, I am wondering if it makes sense to drill two holes again, or if the head intake thru-hull can be shared with the sink drain, i.e. only requiring one hole? I was thinking to put a V-valve after the seacock with one end going to the head and the other to the sink. The end with the sink has a stop ball valve that is shut when the sink is not being drained.
Will that work? Any potential trouble down the road? What do people think?
New York City