You may not be able to have everything you want...
Good quality y-valves have a "barrel" inside that the handle rotates to open one side or the other...solid, sturdy, pretty much leakproof. Whale puts a 5 year warranty on 'em. Jabsco y-valves, otoh, just have a VERY flimsy little "gate" inside that the handle swings from one side to the other. A bit of TP or something like a watermelon seed (don't pretend you NEVER swallow any!<G>) caught under can break it or jam it...force the handle, and you can break more than that. And...they leak after only a little wear! It's nice to be able to lock a y-valve...but better to have one that will last more than year or two--if that long. The easiest way to lock it: drill a hole in the handle big enough to run a plastic tie wrap (keep a supply on hand) through. Or replace the switch for your macerator with one that requires a key. However... The thru-hull should ALWAYS be kept closed except when actually dumping the tank too...and your seacock doesn't have a locking feature. So not having a locking feature on your y-valve shouldn't be THAT much of an inconvenience after all! Btw...shop around for it. Prices are all over the wall..WM is by far the highest.
