About 10 minutes after flushing, the entire bowl is nearly empty, just inch or so of water at the bottom. The tank empties and fills fine. There is no water leaking on the floor. Is this a simple fix or is this a sign of a larger issue (i.e. Crack below foundation)?

Did you clog it recently? There is most likely something hung up in the trap of the toilet that is slowly wicking the water from the bowl. It happens sometimes after the toilet was clogged and not everything makes it out of the trap. Try plunging the toilet or dumping a 5 gallon bucket of water or two in the bowl as fast as it will take it. If that does not work you will need to snake it.

Remove the toilet tank lid and see the small refill tube it should be connected to the overflow tube see the images below, good luck.

John

About 10 minutes after flushing, the entire bowl is nearly empty I have a different take on this. There are a few things that could take your level down. There could be a crack in the bowl letting the water seep out over twenty minutes. That would be my first guess. My second guess is kind of far out but since I've had a couple of calls that lost water in the bowls, I'll throw it up for grabs. The water in your bowl is a trap/seal and connects directly to a pipe called a vent located on your roof. If that location is windy, it has been noted that the wind blowing over the vent pipe causes a suction that syphons the water out the bowl. But that's rare and you will notice the level raising and falling as it happens. I'm going to go with door #1 if only because of the time it takes for the level to go down. There could also be a factory defect in the bowl. Sometimes in casting the bowl there is a small bubble in the china. Instead of junking the bowl the manufacture will put a porcelain patch over the hole and send it on through. On occasion the patch will fail allowing the water to seep out of the bowl. If that's the case you would have a full bowl after you flushed and the bowl filled but some time later you would notice a drop in the bowl level. The only other thing might be if you dropped something in the bowl and cracked it. If you're worried about where the water's going, in both cases it drains back down into the sewer and not under the bowl on the floor. To check the bowl must be pulled, filled and put up on saw horses. You can then see if there's any leakage from the bowl.The only fix I know is to change out the bowl. The only bright spot is that it's possible that you won't need to buy a whole toilet assembly, a large plumbing shop should have bowls that will match your old tank. If you decide to do the work yourself, click on back and I'll walk you through the installation, Good luck, TOM