I plan on calling a plumber, but in the meantime curiosity is killing me. My laundry is upstairs. Currently I installed a new washer. Everything has worked fine except last night I noticed some water damage along where the wall meets the ceiling, directly under my washer. There isn't any leaking under or around the washer. I have a standard drain in the wall (shown in picture one) which seems to be working fine. Also, I have a horizontal pipe running out of the wall and emptying into a floor drain. Upon closer inspection, this floor drain was backed up with water. I've never seen water dripping from the pipe into the drain, nor have I ever seen water in the pipe. I've ran the washer, flushed every toilet upstairs, ran every sink upstairs, and every bath tub upstairs and nothing effects neither the backed up water in the drain or the pipe coming out of the wall into the drain. Also, I've tried running a coat hanger and it seems to just get stuck at what looks like a 90 degree turn in the drain pipe about 6-8" down. Also, I measured the spot where the leak in the ceiling is and it's exactly where this drain is. My questions: what's the purpose of this drain? I know a lot of upstairs washrooms have drains in case of an emergency, but what's the pipe for? Is the clogged drain likely the culprit of my ceiling leak? Thanks and any help would be appreciated.

http://i.imgur.com/D2IdG.jpg
http://i.imgur.com/AG30o.jpg

Two things:

1. The obvious question is: Referring to the pipe in Picture AG30o, does the pipe continue horizontally through the wall, and if so, what's on the other side of that wall? If not, is there a floor above, and if so, what's above your laundry room?

(Is it possible that this pipe carryies condensate from an air conditioner or water leakage from a hot water heater?)

2. The problem I've found with floor drains in laundry rooms is that they seldom get used, and the result is that they'd get clogged up with lint and dirt that falls on the floor. If I were you, I would take a wet/dry vaccuum cleaner and put the suction hose right over that floor drain. Hopefully, you can suck the clog out of that drain line.

Have you contacted the previous owner of the house to find out what that pipe is all about?

This message has been edited. Last edited by: Nestor,

Go on the roof and check the seal around the vent pipe coming through the roof in that area.
It's very common to have the seal fail and water can then run down the PVC pipe and ends up causing damage around the base of the wall.
They make a very simple to install rubber ring that just slips over the PVC pipe that's made to fit tight on the pipe and is made much bigger then the old seal so you do not even have to mess with the shingles trying to change the whole roof jack.
DO NOT JUST TRY AND CAULK AROUND THE OLD SEAL! Your just going to make a big mess and make it harder to repair it right.

get some white cloth, paper towels, etc... and squirt some food coloring into a glass of water. put the cloth between the silly pipe and the floor drain. pour the water into the washer station's drain slot.

if it comes out of the silly pipe and colors the white cloth, you have a stupid DON'T-it-yourself job here.

let us count the ways this is wrong as you run a snake down that floor drain to get it cleared....

(1) there are so many ways to flood the laundry room here I can't count them all. every pipe should be firmly connected to something that leads to the right place.

(2) and the right place comes from the basics of plumbing. the basics of plumbing are three... water goes up, (!) goes down, and (the gas) goes out the roof. as long as each item does only that, you should be legal.

(3) the minimum drain size for a washer drain is an inch and a half, for the spin cycle or a broken inlet valve will allow enough water to flow fast enough to require at least that large a pipe to drain it reliably.

(4) and there needs to be air after water... the weight of water running down the line is such that it will pull the safety water out of drain traps, letting flammable and suffocating fumes into the house from the sewer. air after water is provided legally by a vent line no smaller than the drain, going up through the roof. pouring water into a floor drain because you can't figure out how to cut drywall and glue pipe does not do that, it just provides an air break so you can't siphon sludge back into the washer.

it's all bad. what should be done is to open up the wall carefully so you don't cut any pipes or wires, after verifying the drain is wrong, open a little ceiling below if needed, drill a hole, and run a pipe and a waste T into existing drainage.

if the floor drain is now snaked and running clear, try the colored water test.