JoeSpareBedroom wrote:

Or maybe not a leak, per se. My first floor toilet began running constantly
between flushes 3 days ago. Not full blast, just a trickle to remind me of
how I'll be spending part of my Saturday. Or so I thought. Just noticed a
small puddle in the cellar below the toilet. It's the sewage pipe that's
wet, but the puddle smells clean. My first thought was that the supply pipe
got so cold from running constantly that what I was seeing was condensation,
but as far as I can see (because part of the supply pipe's hidden), that's
not the case.

Next thought: The cold water contracted part of the sewage pipe assembly
enough to leak. But again, based on the lack of smell, that's not it.

Nightmare thought: Wax ring. I don't want to think about that.

There's little or no condensation on the tank itself, and the floor in the
bathroom is dry. Luckily, it's not humid here today.

The damp drain pipe is probably a red herring.

If the leak is not the flush valve or it's seating area, check the
overflow pipe if it's metal. I have seen a brass overflow pipe develop
pinhole leaks at the bottom where it threads into the flush valve
assembly and some of the thinner threaded areas are exposed and it
pinholes in that area. Next suspect after that is the two tank bolts and
the rubber washers that seal those. The tank washers could also result
in a leak that runs down the back of the toilet and could appear below.