I have a leak underneath my upstairs bathroom that shows up on the living room ceiling. The leak shows up randomly (the last time we noticed it was about 3 months ago) then it does not happen again for awhile. What could be causing this random leak? We have tore open the ceiling twice now and have not been able to catch it when it leaks. Help!

Could be a vent boot. Notice it when it rains a lot?

Not really. It rained a few days ago. Would it take a few days to show up?
It really is random when it happens.
I was thinking about a rain pipe as the culprit but wouldn't we see it every time it rains then?
There is no pattern to this leak as far as we can tell.

The water leaking into the ceiling would be where I started./ I'd open u
P the ceiling and start running. Flushing and draining until moisture showed up. I wouldn't over look running the shower stream against the tile to see if the grout was leaking. And if you have young kids don't forget that they splash. Have I misses anything? Good luck. Tom.

Do you by any chance have one of those, what use to be called, pulsating shower heads. The kind that you select different shower streams?

No kids. Trust me, it is not because of splashing or overflow. We had done all of that- running the water, flushing and running the sink and there was no moisture when we did that. Like I said, this is so random and we have not been able to catch it when it leaks... it's so frustrating.
We do have pulsating shower head but it is new and the leak had started before that. Plus we do not use the different settings.

Suggest you pull the escutcheon around the shower arm away from the wall and look inside the wall for signs of a water leak. If you find any signs of a leak, new or old, remove the shower arm from the drop ell. Coat the threads of the shower arm with a generous coating of pipe thread compound and reinstall. I prefer thread joint compound to Teflon tape for situations like this.

When reinstalling the shower arm use a good strap wrench to avoid marring the finish. Remember the arm must point downward. Before starting the next turn you must decide, from the resistance, whether you can make a full turn. If you can't make the full turn you must remove the arm, re-coat it with joint compound and start over. You can't just back it up.

The pulsating shower heads cause a lot of problems, I would remove it and smash it with the biggest hammer I could find. But that is just my opinion.