We have had a few comments on the subject of leaking vents. The main question is this. If I go into my attic during a rain storm under what I know is a damaged vent, why am I not seeing any water?
The answer is that the vent is likely just leaking water into the decking and under the shingles, and not enough water is leaking to form a drip. This is really a long term problem, because decking is plywood, and although plywood may be water resistant on its surface, the water is actually soaking the wood through its thickness. Plywood has minimal resistance to water at the glue layers that make it, and they rot easily. So over the 15-20 years or more between re-roofs, tremendous damage can be done to the decking and it has to be changed at a large cost. In fact, we just had a customer tell us when she re-flashed she was charged 950 dollars for decking repair.
A Critter Quitter costs a lot less.