Shower Wall Leak

In the middle of a bath remodel. Had everything down to the studs. Now that all walls are all back up and I am ready to tile I noticed water on the floor. Water is leaking from the bottom of the drywall on the back of the shower. On the other side of this drywall is the shower plumbing. This wall has been up for a month and just started showing signs of a leak. What would cause a leak when we are not using any water in the bathroom at all. The toilet is not in yet and the shower has not been tiled yet. Could it be that the pressure built up in the shower pipe and that is why it is just now leaking, should I turn the water on in the shower to see it the leak goes from a drip to a drizzle? Help

Thanks to everyone's responses. I took the drywall down and the leak was in the shower pipe where the new shower head fixture was installed. The contracter who installed the fixture will be repairing the pipe and the wet drywall. Thanks Again!!!

Are you sure a screw or nail , during wall board installation , wasn't driven into a water pipe.?

You're going to have to open up the wall (front or backside) to fix whatever's leaking, so go ahead and open it up and you'll see what's leaking. (You may be able to see enough by removing the shower valve trim.) Assuming the water to the shower is turned on, and it's a new shower valve, my money would be on a threaded connection at the valve.

leak

It would be an unusual connection of any kind that waited a whole month and then leaked enough that you could see it. My money is also on a nail or screw. I had one yesterday where the cabinet installers were placing a shelf in a nook in my neighbor's bathroom. (This is a home remodel/addition that has been going on for a year now), and could not get their nail to penetrate my protective nail plate so they moved the nail sideways to miss it and hit the water line dead center. The also had two others that were aimed at it, but were too short because of the angles.

I like the nail theory, but have an innate distrust of threaded connections, particularly with all the cheap-crap Chinese fittings out there. I tried for days to get a 1/2 x 1/4 reducing bushing to stop leaking at the 1/2 end, and eventually gave up and found a US-made fitting that worked. Maybe it's a Metric thing.

Rereading the OP, she asked, "...should I turn the water on in the shower to see it the leak goes from a drip to a drizzle?", implying it's a pretty good leak. Also not clear whether the supply to the shower is on or not, but I suspect it is. In any case, she might be looking at some drywall replacement.

Whatever it is, it apparently took a month to show up, so it's not going to affect the water bill .

I had the same thing happen in my shower. The problem was a poorly soldered connection to the shower valve. Fortunately, I was able to access the back of the shower to monitor and catch this leak b4 it did any damage.

Thanks Everybody

Please let us know what you find; lots of money riding on this .

Conclusion

The leak was where the new showerhead fixture connection was. The copper fittings were sautered or soldered , but it still leaked water.

On a non-plumbing note, tile over drywall in a shower? Please tell me there is Kerdi in between. Tile right over greenboard in a shower area is no longer code in many areas, nor is it a great idea.

(Disclaimer: I am new here and by no means a professional . . .)