I've always been in the "shut" camp, because the P/O told me to do that.
however others alluded to they don't shut the ac valve ever and it works just fine.
Tested it out today... checked the mid bilge where the AC water pump was before leaving.. left valve open.. result = 5 gallons of water in the mid bilge (salt) after a short trip.
Is this normal? I've been on other boats with AC where they don't do anything at all, which is why I figured I'd test this out.. appears I have a leak when pressure builds up? Any thoughts are appreciated.