My wife was showering this morning, quick shower, 5 minutes, and 10 minutes later we noticed downstairs dripping through the ceiling onto our laundry machines. This is right underneath the shower.

No accessible plumbing lines. It is a cube-shaped shower with a tile floor. To troubleshoot, I shut the water off to the house when we went to work. When I came home from work, I first turned on the water to the house. No drip after 20 minutes. Then, without turning on the shower, I poured about 10 gallons of water right down the drain, no drip. Then I turned on the shower head and pointed it directly at the drain, no drip. So I'm confident that the leak is not in the drain line, nor is it in the plumbing line to the shower.

So I'm thinking now that the problem either only happens when somebody is in the shower, thus putting pressure on the drain pan (which also, is not accessible without tearing the shower apart)... or it is simply a leak in the grout or tile someplace that happens when water hits parts of the shower other than the drain.

I will try and troubleshoot further when my wife gets home, but thought I'd throw this out there for now. Thoughts? Thanks!

Your guess is the first thing I would have suggested based on your post. Only guessing the flexing is upening up a crack enough to allow water to enter. Look at everything well with a flashlight and nobody in it... then have her stand in it and do it again... see if you can notice something you didn't see before.

First thing I would suspect would be a leak where the shower arm screw into the shower riser pipe. Especially true if you have a pulsating shower head.

Suggestion.

Stop by hardware store, pick up a 1/2" PVC pipe cap. Remove shower head from shower arm. Screw pipe cap onto shower arm, a little more than hand tight. Turn on cold and hot valves. That will test your entire supply system. Leave pressure on for 30 minutes.

If you get water downstairs it is most likely from where the shower arm screws into the drop ell of the riser pipe. Pull escutcheon around shower arm away from wall and look inside for signs of water.

No sign of water around shower arm, remove handles and valve stem covers, look for water around valve stems.

Fleetmack,
You are on the right track. Good trouble shooting starts with identifying all possible contributors, and then use an orderly process of elimination to find the cause of the leak.
I suggest you plug the shower drain, and fill the shower base with water up to the top of the entry saddle - this will prove the integrity of the tiled floor, drain pan connector, and the lower wall tile and grout joints... I also suggest opening the ceiling below; patching and painting is not a big job, and it will help to dry out the affected area, and may also reveal some clues about the leak...

Thanks all. We didn't work on this further last night. It isn't a HUGE rush as we have a second shower, and it only leaks when someone is in it. Regardless, I need to get this fixed soon.Thanks all for suggestions. Mike45plus, I am going to try your suggestion tonight. Plug the drain and fill the shower basin with water to see what happens. I am not a plumbing genius... or even novice. What I've typed above is about the limit to what I know about plumbing. That being said... If I plug the drain, fill the basin, and have no leaking, that would mean everything is in tact when nobody is in the shower. But that would mean I cannot reproduce the problem... leading me to believe it only leaks when someone is standing in the shower. If this turns out to be the case (only leaks when someone is standing in it)... would that prove, or at least strongly hypothesize, that the drain pan is bad and we need to rip the tile out and reinstall a drain pan?

Don't condemn the shower base / pan until you've tested it. There are other tests that should be performed - try connecting a hand held shower / hose in place of the fixed shower head, get in the shower with the door closed and direct a stream of water at all the wall penetrations, and aim a stream at the shower door, trim, and threshold. Water can escape the confines of the shower, and end up on the bathroom floor where it may find a path to the room below via a loose caulk joint, or, even under the toilet...

Hi Fleetmack

I would suggest plugging off the shower pan as suggested by Mike45, but I would use not use the shower valve to fill the pan with water...I would use a 5 gallon bucket and fill the bucket from a nearby tub or sink and fill the shower pan that way. By attacking the filling of the pan in this manner you can be sure that if a leak appears it is from the shower pan/drain and NOT from the shower valve, right? If the pan test fails to show a leak then you drain the pan and test the shower valve and shower head next. Here, you remove the handle and trim plate from around the shower valve and you turn the shower valve on and using a flashlight you inspect inside the wall to see if water is dripping from above the shower valve (suggesting shower arm/connector may be the problem) or at the shower valve itself. If the shower valve has a diverter to control shower water volume, slide that back and forth during the test.

Start there and let us know what you find, OK?

Mark

Thanks for the tip, will work on this over the weekend and let you know what I find out. VERY helpful tips all around, thank you all!