Leaking 2nd story shower mystery

When I bought my house the previous owners made no mention, and the inspector didn't find any evidence of a leak.

The shower has a hand held sprayer, a high wall mounted sprayer, and three side mounted sprayers.

You can select one or many of the sprayers with a selector knob.

There is an access panel where I can clearly see and inspect for valve and pipe leakage in the adjoining closet for all except the wall where the three sprayers are.

Directly underneath this floor is a garage with clear access to the subfloor.

You can go in the shower stall (an enclosed fiberglass two sided wall/floor) and take a shower and maybe three of four times it won't leak a drop.
Another time you can take a shower and it leaks buckets.

We have restricted our sprayers to only the hand held sprayer to try and rule our a specific sprayer.

Standing on a ladder in the garage, I wrapped all the joints with silicone tape to rule the joints out. (Still leaks)

In the garage on the subfloor over my head I checked the tightness of the collar nut (my words, I don't know what it is called) and it is so tight, I can't loosen it.

The water doesn't seem to be coming from the exact location where the drain pipe is though. It seems to be coming from somewhere else away from the collar perhaps between the shower basis and the subfloor, but leaking around the drain pipe. I may be wrong about this, it is very difficult to tell.

I put silicone in the drain part above the black rubber looking gasket that is around the PC drain pipe under the drain grid to make sure that it is sealed.

Last year I replaced the valve that controls the sprayer selection hoping it might be the cause.

Short of completely removing the stall to try and find the leak, I can't think of anything to try that I may have missed.

Any guidance will certainly be appreciated.

For what it is worth, I have tried to get a plumber in here twice, but each time, after waiting a few hours I get a text message saying they won't make it, and never a follow up call to reschedule.

Thanks,
-= BDM

hard to say, it sounds like it is the connection at the shower pan

in this area, you have 2 places to look for a leak

first buy one of these. remove chrome strainer, pop it up/off

http://www.supplyhouse.com/Matco-Norca-TP-08-2-Wing-Nut-Test-Plug

insert it in the drain pipe and fill the pan with water.

this will test the connection of the drain body to the shower pan

and the connection of the pipe to the drain body

I just ordered the test plug. based on what I have seen before, I am guessing it will show up as leaking from the pan to drain.
I'll update once the part arrives and I've tested. (Should be here Thursday)
I tried to loosen the collar nut (my name for whatever it is called) and couldn't get it to budge. Subfloor prevents my special tool from getting on the notches, and pounding on it with a screwdriver seemed like it might not be the best way to do it.
Thank-You.
-= BDM

I have been in your situation, I took a piece of 1/8'' steel and cut it like so

stick a screw driver in the hole, to turn the wrench

You mention the shower stall is 2-sided with a floor. Are the other sides enclosed at all? In my home, I had a tiled sill on which sat a glass door. The sill leaked like crazy and ruined the basement ceiling below it. I thought it was a valve leak at first, but I learned that the glass door to sill interface is notorious for causing leaks.

Frodo, Thanks for sharing the great idea. I may end up needing to fabricate the same thing.
Masterjer, The door is built in as part of the enclosure. I should have been more specific, it has two sides adjoining walls, then a portion that sticks out with a door attached. It is all a single enclosed fiberglass 'booth' like shower stall. If needed I can upload a picture. Looks like my plug should arrive Thursday. Took a shower in it last night, didn't leak a drop.

Hi Frodo,
Have you ever seen a tool like what you made that can be purchased? I've looked at a bunch of plumbing sites and haven't found one like your yet. I can imagine me trying to cut this to fit with a hacksaw.
-= Bruce

This was an interesting experience. I installed the drain stopper, and had no leak. To rule out any of the valves and pipes, I filled the shower basin with a 5 gallon bucket. As the level of the water got above the lip but still should have been contained, water started leaking through the shower stall wall, out on the floor. I checked downstairs and sure enough, it was leaking down through the subfloor. I looked where there should have been caulk and a pink milky gooey substance came out when I pressed on the metal. I don't know what it was, but it wasn't any caulk I have ever seen.
I let everything dry up, caulked it, and my wife and I took several showers over the weekend, I ran the water up against the glass panes that let water run down to where the leak was. We never had a leak.
I would say the problems was in two parts. 1.) The shower stall wasn't effectively caulked, it is now. 2.) The tile floor is very nicely done, but is grout only, no caulk against the shower basin or wall, allowing any water on the floor to run down into the subfloor.

Thank-You for your help folks.

-= BDM