I have a tile shower on the second floor. I noticed some water stains around the light fixture below it on the first floor.I regrouted the bottom of the shower so there should be no leaks there. I ran a snake down the drain and it seems clear. I took down the light and it still leaks after taking a shower. It is not a large leak only a puddle of water the size of a 50 cent piece comes down from the ceiling box. I also looked down the drain and do not see anything but water sitting in the drain. Is the wtaer supposed to be sitting in the drain? Do I take down the ceiling to check the pipes for leaks?

YES.. the pipe should have water in it. This is a p-trap and it is wetted to keep sewer gases from coming out of drain line and into your home.

Start at the shower valve first... if single handle shower valve remove shower face plate and see what happens when you run shower... look behind, down, and up toward the shower head when the plate is off wall... what do you see? IF you have 2 handles... do same.. remove handles, chrome plated parts and then run shower and see what happens.

If nothing obvious... then.. I am afraid I must begin with questions... So is this a canister type light near leak? 'Cause some of these can be loosened/moved aside to allow better access to really see what is going on up there. If not canister type... you said something about ceiling box... is this screwed into a joist.. can you remove this and push to left or right (turn off electricity to entire house unless you can identify positively which fuse/breaker belongs to that box!! )??

If none of that is possible... then yup.. will probably need to access the ceiling somehow. One place to start here would be to cut an access panel into the ceiling... even if only temporary and you will patch later... home depot sells a great spring loaded access panel in various sizes... so can start with say an 8" x 8" hole to access work... and then if a problem that can be fixed.. could go larger and again just clip in access panel to fix ceiling for now... fix later.. or of course, patch ceiling immediately afterwards.

Then... lets say you have opened the ceiling near light.. and want to explore the leak further... hopefully you will shine flashlight up and find leak immediately and it will be easily fixed. BUT if not... there are a few steps to take to see if it is shower drain or shower copper pan... get back to us with some answers and we will see what we can do. Let me know if this helped!

I have a tile shower on the second floor. I noticed some water stains around the light fixture below it on the first floor.I regrouted the bottom of the shower so there should be no leaks there. I ran a snake down the drain and it seems clear. I took down the light and it still leaks after taking a shower. It is not a large leak only a puddle of water the size of a 50 cent piece comes down from the ceiling box. I also looked down the drain and do not see anything but water sitting in the drain. Is the wtaer supposed to be sitting in the drain? Do I take down the ceiling to check the pipes for leaks?
I know it is the drain because I poured 4 big cups of water down it and it leaked, only one drip. It is a ceiling box that is nailed in, so looks like I am cutting a hole in the ceiling next.

You know it is the drain... but could be the joint between the shower drain and the shower pan... or it could be leak between shower strainer and p-trap... open ceiling and see which it is (latter is better). ANd, cut a square and then can use one of those access panels to buy you some time until you are sure what needs to be done. Good luck!

Thanks fpr the advice, looks like saturdays project. Oh boy!