Roof Leaks Are Usually Not Visible

One thing to remember about leaking vents, most home owners wont see any leak regardless of how much its raining outside, short of a hurricane. This is because the leak will run down the outside of the vent pipe and the inside of the flashing and most likely be absorbed by the plywood decking under the shingles. Over the years this will rot this decking and will require replacement when the roof is re-shingled. So if your vents look like that one on the home page, (my house btw) you got a leak whether you see it or not.