Fortunately - I was still up at midnight and heard the splat, splat, splat fairly soon after the toilet tank developed a rim to bottom crack. The toilet already had a valve problem and would have kept trying to refill the tank until the inevitable, middle of the night, barefoot, splat in the flooded bathroom. I turned off the water, mopped with several towels, found a heater to dry the floor/wall joint and went to bed. Normally waiting until we could get a plumber would not be that much of problem but, Dave is taking "water pills" as part of his post-op cardiac surgery treatment.
Fortunately - we have really good friends! Especially one who after remarking "be sure to let me know if there is anything I can do for you" came right over to fix our toilet. I went to the hardware store thinking all I needed was a new tank. Seems in the 49 years since ours was installed, they have changed some of the parameters. We now have a new toilet and Lowes has a cracked tank in their dumpster. (I wish I had taken the whole thing with me).
Matt, who changed out the toilets in a very crowded bathroom complete with three curious Chinooks, left Dave this card:
Fortunately - really good friends come with a good sense of humor.