Thanks Rick. The cheap little valve in my home toilet will work for 30
years but on a boat "Y-valves don't work under pressure"....you really
can't make this stuff up!.

I'll look for a good valve. If that fails I guess I can just put in two
regular valves on a "T" - this would have the advantage of turning off
all water to the head (assuming I can remember which way to set them).

Carl