We noticed water damage on the kitchen ceiling. We cut out a piece of the ceiling and saw that the drip was coming from around a PVC pipe. On the second floor directly above the leak is a sink and vanity. All of the pipes seemed dry so we pulled the sink and vanity and cut open the wall.(This is an exterior wall) The insulation was soaked and molded. The copper pipes are below the water damage. It seems like it is coming from the PVC pipe. Should we assume that it is a stack pipe problem and call a roofer or a plumber? We are trying to find the problem ourselves but aren't having much luck. We would appreciate any advise you could give us.
Thank You, Simbalay

Are you using plenty of light and maybe a mirror to see in the areas where the leak might be? Have you removed the soaked insulation?

Not sure of the picture totally, but although water can't run up hill, it can be wicked up. If the PVC pipe goes through the area it might be a leak at the roof running down that pipe? A good way to check for that would be to dry it off up as high as possible and tape a lot of dry tissue paper around it for a while to see if water is getting to it at that point. Have you checked in the attick for any water damage around the PVC pipe... if you have an attick?

It does sound like water is flowing down the PVC pipe from a leak at the roof.

One more question is if the water drains from the sink toilet and bathtub without any leakage through the PVC pipe? It could have a loose connection where the water could escape if there were enough water in the line it could possibly back up and leak there... so let it run for a while... also run anything else that may be up there using water such as a washing machine... if you have anything like that using the line. I had a bathtub leak like this from an overflow that was not hooked up properly, but it only leaked when the tub water went above the overflow outlet... not through the normal drain.

I like the way Ohioguy thinks. Go in the attic and check the roof vents for moisture. This is the first place I would check. Let us know what you find. Regards, Tom