This is a disconnected plumbing vent pipe in the attic of a ten year old home. The purpose of the plumbing vent pipe is to equalize the air pressure in the drainage system so that water will drain properly and to vent sewage gas to the exterior of the home. In this case sewage gas is entering into the attic and the portion of the pipe above the roof is allowing rain water to run down into the attic (the owner couldn’t understand why he had a water stain on his kitchen ceiling.)
