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Copper vent pipe corrosion

2006

I recently did a copper sewer pipe replacement.
The 3 inch pipe had green flaking stuff on it with holes all over the pipe.
The drain copper pipes are starting to do the same.
Me and my boss are wondering what may be making the pipes corrode this badly.

Jack Rayburn Jr
Plumber/Electrical - Davenport, Iowa

I would assume the vent pipes were attacked by sewer gasses (methane) from the inside out. I haven't heard much about copper used in drainpipes, it does not sound practical to me. Drainpipes carry so many things like acids, alkaline based soaps, grease, all reacting with each other, no wonder you had to do a replacement. I hope the homeowner chose something more affordable and efficient for a replacement!

Mark Baker
process engineer - Malone, New York
2006

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January 19, 2011

I have the same problem on my 2 story residential 3" vent, it starts at the second floor where two 45's offset in the wall to go thru the roof and appears to be corroded the entire length above the first 45. It only has corroded the copper (the short piece of copper that joined the two 45's was completely gone)and not the fittings and there is no apparent corrosion below the first 45 down to the first floor. I cut out the corroded pipe and replaced with PVC.
Part of the problem may have been flux at the fittings but the rest had to be gas either ammonia [on eBay or Amazon] or methane.
If anyone knows how to prevent this or if further inspection of the rest of the system would be needed or has an explanation or advise it would be appreciated.

Mark Williams
Mech Contractor - Corpus Christi Texas USA