You know ... "Parts is parts." Well, they ain't.
My guest toilet hasn't worked for quite some time. I tried to fix it, but in the process, it began leaking between the bowl and the tank, but only when I flushed. Did I say "leak"? I meant "flood". So I wrote that off to incompetence and resolved not to fix my other toilet unless I had to ...
and then one day, I had to. The cheap-ass parts inside finally gave way, so it was time. I put it off until guests were scheduled to arrive (you know you can use a toilet without flushing, right? Two ways: dump water quickly into the bowl to force the contents down, or you can also fill the tank manually and flush like you would ordinarily), but guests probably don't want to do that.
So off I go to Lowe's to pick up a toilet repair kit. It's pretty easy to replace the fill valve (the one on the left side, for most people), because you just unscrew what holds the pipe in place, pull the old valve out, put the new one in, adjust it, screw the pipe in place, and you're done. If you have to replace the flush valve, then you've got to take off the tank ... sigh. Not fun. (It's more challenging if you have one of those things that sits above your toilet ...)
So I get the pieces in place (except for one that stops leaks – I figured that out shortly before the end of the story), flushed to test, and hey! There's that flood thing again. I put the tools down, come back out to the living room, and play some more keyboards for a while.
Once I've calmed down, I Google "Fluidmaster leak between tank and bowl." Not quite helpful enough. Then I hit another thread that suggests something about toilet types. Hmm. And finally I found this one. Some toilets need bigger gaskets ... hmmm ... I'd better go check.
Sure enough, both toilets are Gerber toilets. The last guy to post says that he kept his old gasket, used the rest of the new parts, and it worked. I do the same. ta da!
Problem solved. Back to the store I go tomorrow to get a gasket (hopefully) for the other toilet.
Parts is not parts.