Toilet blew up on us

Well, I guess it didn't actually explode, but the toilet on our main level has been leaking more and more rapidly from the top tank into the basin. I tried adjusting the mechanism (it has some sort of fancy job that shuts off when the tank is full and doesn't turn the water back on until the handle is pressed again) and a few simple fixes I found on the internet, but nothing cleared it up. So we broke down and picked up a complete tank repair kit from Home Depot over the weekend. The guy at Home Depot said we probably wouldn't need the complete kit as he didn't think the problem would require actually taking the top tank off since the water wasn't leaking onto the floor. But I didn't want to make more than one trip and it was only $10 more for the full shebang.

Based on the stuff I had already tried and inspecting a few of the pieces I really didn't think it was a problem with the flapper or overflow tube. I thought it was possibly the rubber gasket that sits between the tank and the valve the flapper closes over. Turns out to look at that you do have to remove the top tank! Once the top tank came off the problem was pretty clear. The rubber gasket that sits between the top tank and basin was pretty well rotted (different from the one I initially suspected.) Even though the problem seemed clear, I still swapped out everything for the new parts. Based on about a dozen warnings throughout the instructions to not over tighten any bolts or the porcelain may crack, I tightened everything up sort of tight and gave it a go.

Of course, now the thing leaks all over the floor! So I disassembled the thing once again and took my chances with cracked porcelain by torquing everything down nice and tight. This time the toilet held it's water and it's been working fine since.

Decided to check the other toilets in the house, which all have normal guts so they would just constantly top themselves off if there were a leak. Turns out the toilet in the master bath has the same (although much slower leak) problem, but the other two are fine. Tried cleaning out any gunk between the flapper and the valve it covers (wasn't much) but that didn't fix it. My bet is the exact same gasket is rotted. Guess I'll be tearing it down this weekend!