Where can I find install instructions for...

the Toto THU013Z flush valve? I got interested in what holds the flush valve into the Ultramax and if the "O" ring seal ever goes bad how you replace it.
I see two screws in there, but I wanted to understand the anatomy better. In a one piece, I guess if the "O" ring goes bad it's like if the flapper goes bad, water leaking out of the tank to the bowl? I've been looking online, but for some reason I can't find it.

Lee

http://admin.totousa.com/Product%20Downloads/PD-00346,%20MS854114S_MS854114SG,%20V.01.pdf

There are two brass wings that hold the flush valve to the tank.
When you loosen the screws (careful not to loosen then all the way) one of the wings swing inward and you can pull up the flush valve. Hard to explain but one you do it you will understand.
There is a gasket (o-ring) underneath and that can be replaced.
I haven't seen them going bad over time they usually need to be replaced on brand new toilets if they are pinched.

Thank you Peanut, exactly what I wanted to know. I think I can picture that now that you explained it. I was picturing either that, or an arrangement where one side hooks in and the other side screws down...

I haven't seen a bad seal there yet, a couple times the brass wings needed tightening to secure the flush valve.

Thank you!!!