Short answer
A leak around a roof vent pipe is usually a cracked rubber boot, the collar that seals the pipe to the roof. Look in the attic for wet wood along the pipe, and from the ground with binoculars for a split or loose boot. Set a bucket on the joists under any drip. A roofer can replace the boot, usually in a short visit.
Safety first
Stay off the roof. In the attic, step only on the wooden beams (joists), watch for roofing nails poking through and keep away from wiring.
How to spot a leaking roof vent pipe
1A stain shows up near a pipe
Often over a bathroom or the kitchen. The pipe sticking out of the roof is the plumbing vent, and its seal can crack.
Read all the steps
- A stain shows up near a pipe. Often over a bathroom or the kitchen. The pipe sticking out of the roof is the plumbing vent, and its seal can crack.
- Follow the pipe in the attic. With a flashlight, look at the wood and insulation around the vent pipe. Wet or dark wood means rain is running down it.
- Check the boot from the ground. With binoculars, look at the rubber collar around the pipe. Cracks, gaps or a missing collar let water slip in.
- Catch the drips in the attic. Set a bucket or a tray on the joists under the drip, and pull back wet insulation so it can dry.
- A roofer replaces the boot. A new boot slides over the pipe and tucks under the shingles. Do not climb up to caulk it: that rarely lasts.
- Cracked boot? Call a roofer Especially if: you see a cracked, loose or chewed boot from the ground.
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Why pipe boots fail
- The rubber dries out and cracks in the sun, often years before the shingles wear out.
- Squirrels and other animals chew the rubber.
- The nails holding the boot work loose and let water under it.
- The boot was set too low under the shingles when the roof went on.
Other causes that look the same
- A bathroom fan duct that drips condensation in cold weather.
- A leaking drain or supply pipe in the wall or the ceiling (call a plumber).
- Missing shingles or bad flashing higher up, with water running down to the pipe.
When to call a roofer
- You see a cracked, loose or chewed boot from the ground.
- There is wet or dark wood around the pipe in the attic.
- The stain grows after each rain.
- You smell sewer gas inside, which can mean a broken vent pipe (call a plumber).
Frequently asked questions
How do I know if my roof vent pipe is leaking?
A stain on the ceiling near where the pipe runs, and wet wood around the pipe in the attic after rain. From the ground, a cracked or loose rubber boot is a strong sign.
What is a pipe boot on a roof?
A rubber or metal collar that slides over a pipe and seals it to the roof. The shingles overlap it so the water runs past the pipe instead of into the house.
How long do roof pipe boots last?
Rubber boots often crack before the rest of the roof wears out, especially in strong sun. Ask the roofer to check them whenever they look at the roof.
Can I just caulk around a leaking vent pipe?
Caulk is a short-term patch at best, and climbing up to do it is risky. Replacing the boot fixes it properly.
Is a leaking vent pipe a plumber or a roofer job?
A roofer, if the water comes in where the pipe goes through the roof. A plumber, if the pipe itself is broken or you smell sewer gas.