I'm looking for some assurance from any plumbing veterans out there.

I am in the process of remodeling a house that has an occasional leak from the 2nd floor shower. According to the former residents, the leak doesn't occur so long as nobody is in the shower, but as soon as someone stands in it, a nice drip develops in the kitchen ceiling below.

I assume that there's a problem where the drain meets the drain pipe: Is it not sealed properly, so when weight pressure is applied to the shower pan, the gap increases? I'd like to replace the shower unit that's generally in poor condition, but before I go through all the trouble of installing a new unit (incidentally something I've never done), I want to be more sure that the leak should stop with the new unit.

With my luck, I can only imagine that I'll go through the misadventure of replacing an entire shower only to find that the leak was in some other yet undiscovered problem in a wall that will need opening up behind a newly installed shower.

Thanks for any assurances or ideas,
The Willing Beginner

It is certain that the pressure of someone standing in the shower is moving something and causing it to leak... but it might be someplace else. If where the drain meets the drain pipe is secure, it could be pushing on the next joint down the line... or even the next one after that.

I'd only give it 70% or so certainty that the problem is where the drain pipe meets the drain.

I'd get it exposed first - so you can see exactly where it's leaking.

Do you already have any access holes cut either in the wall behind the wall of the shower that has the faucet and drain - or in the ceiling below it on the first floor? If not, the first place to try is behind it. How accessible is the space behind the shower?

I agree with rick, for peace of mind, expose the ceiling to see it for yourself. It's not a large job to patch a 6 x 6 hole (or smaller) rather than replace something your not 100% sure of.

Yes I will agree, the pressure could be pushing the pipe to a loose joint anywhere along the line. ( possible)

But your opinion does sound fairly reasonable. If you are going to tear the old shower out anyway because you want to, you should be able to see more in the area.

Do remember the place you see the leak in the ceiling is not always exactly where the water is leaking at, the water can slowly follow the outside of drain pipe and leak further down.

Now another issue is if there has been "leak" in the ceiling , i.e. your floor upstairs, there can also be mold, rotten wood and all sorts of other trouble you will find once the shower is taken out.

Thank you all for the help. I will use the suggestions from all three: tear out the shower and inspect along the drain line as is visible, and, if not satisfied, do some ceiling demolition! I'll update after a few days when I can get to the project.

Thanks again,
The Willful Beginner

There is a possibility that the water is splashing off the body of someone in the shower and going down between a soap dish or maybe the escutcheon around the faucet. Also make sure the there is not a small trickle of water getting our of the shower door or tub inclosure, put a dry paper towel down on the floor right in the corner of where the shower meets the front wall... Just a thought.