After 10 years, the caulking around the base of the toilet and the tile floor it sits on started look shabby. So I removed it. Before replacing it, I took a shower. After getting out of the shower, I noticed that the rug in front of the toilet was wet. I thought that maybe one of the two sliding shower doors wasn't fully closed. So I just wiped the floor dry.
Next day, still with no caulk around the base of the toilet, I showered again. Now I could see water oozing out from around the toilet base. The shower nozzle is at the end of a 6' hose, so while standing in front of the toilet I aimed the nozzle directly into the shower drain (about 32 inches away), hoping to see water seep out from the toilet base. That didn't happen.
Next, I removed the toilet and again aimed the nozzle directly into the shower drain, for longer than it takes me to shower. By listening at the toilet drain, I could hear the water running out the shower drain, but no water was visible at the toilet drain.
There is no sluggishness in the shower drain or when the toilet flushes, so I have to rule out a partial blockage past the point both drains merge. Since the house is on a slab, and I only weight 145 pounds, I can't attribute the oozing due to floor deflection when I'm standing in the shower. And there's no seepage when I flush the toilet.
It would appear that the old caulk was damming back the water, but there was no caulk at the back of the toilet because it was too hard to reach that spot. So any dammed water could have escaped at the back.
The old wax ring was still soft and sticky, but there was some black discoloration (maybe mold) at one point. There may have also been a passageway between the inner and outer diameters at this point.
I installed a new wax ring and that was the end of the problem (still with no new caulk). But I can't figure out where the water came from, even if there had be no old wax ring at all.
Possibly there's a tiny leak in the bowl itself, but I don't see evidence, either from leakage around the base or from a lowering of the water level after a few hours of disuse.
Intriguing problem. And ideas? Maybe something bizarre with air pressure in the vent to the roof.