Frozen Vertical Stack Causing Toilet Leak...

In order for a waste line to freeze like that, there must be a blockage tha t is NOT water. Once you have a "cap" on the vent, anything lower than tha t will have problems. You need to clear the blockage (obviously), but see if you can find a plumber with a camera that can go from below to identify what is blocking the pipe. I would do this investigation before the icemel ts though. You should never have a 4" or 5" pipe freeze like that as it sh ould never have standing water in it.

Dan

hat is NOT water. Once you have a "cap" on the vent, anything lower than t hat will have problems. You need to clear the blockage (obviously), but se e if you can find a plumber with a camera that can go from below to identif y what is blocking the pipe. I would do this investigation before the icem elts though. You should never have a 4" or 5" pipe freeze like that as it should never have standing water in it.

In general, I agree. But what if the toilet isn't sealing correctly and has a slow leak? That would allow a trickle which would keep freezing and building, until it blocks completely. I assume this toilet was not used? If it was, then you'd think the problem would have been discovered that way. It had to have been flushed to create the problem. If it worked normally, even if you later somehow cut off the drain pipe, there would not be water to leak out around the seal. Which leads again back to the theory that the toilet has a slow trickle leak that caused it.

I guess the other question comes down to how urgently a fix is needed? It's warmer for the next day or so, maybe it will thaw on it's own. If they had some kind of small immersion heater, that would probably thaw it out faster.