Furnace exhaust pipe exiting a roof
My house is 7 years old. Our furnace is in our basement and the exhaust pipe runs from the basement, up through the first floor, on into the attic, and out the roof. We noticed recently that some water stains are appearing on our ceiling, and after further investigation, we're noticing that water is some how getting into the pipe and flowing down. However, the pipe does have a crown over it, but there is still a gap between the end of the pipe and the crown. It's what the builders had used, and it's what every other house in our neighborhood looks like. Is it possible, and normal, for water to get in this pipe when it rains heavy? I've already gotten up on top the roof and sealed off around where the pipe exits the roof, but it's still getting in and this is the only possible way. Please, I'm asking for someone to ease my mind.
Regards,
Justin