Quote Originally Posted by markts30 View Post
I have seen similar corrosion in pipes...
The moisture in the sewer gasses tend to condense and collect on the upper surface of the pipe...
In the event of copper, the sulfates in the sewer gas form weak sulfuric acid and over time eats right through the pipes...
The acids concentrate in the vent and create nice copper swiss cheese.
How does that explain why only one small section of pipe has the holes?