How to Caulk a Leaking Sewer Roof Vent Collar
- 1). Confirm that the leak is from the sewer roof vent by examining the piping below the vent outlet. Look for dried tracks of discolored water along the pipe and below the pipe seams. Roof leaks can appear on ceilings and walls far from their point of entry, especially if they run along pipes and rafters. After you confirm that water enters your home through a sewer vent pipe, crawl up on your home's roof.
- 2). Peel back the shingles that extend over the top of the upper half of the vent flashing on the bottom of the sewer roof vent. This collar is designed to help hold the roof vent in place and reduce the risk of moisture seepage between the exterior side of the pipe and the roof hole.
- 3). Remove the flashing from the roof surface by pulling out the nails or unscrewing the screws. Turn the collar flashing upside down, and use a putty knife to scrape off particles of cracked and crumbling caulking. Scrape the roof surface to remove the old caulking from the area beneath the flashing. Pick out old caulking from joints along the collar and around the vent cap.
- 4). Squeeze silicone caulking from a caulking gun into the joints that attach the collar to the flashing and the vent cap. Smooth the bead of caulking into the joints with the tip of your finger. Squeeze a bead of the caulking along the underside of the vent flashing. Press the flashing back in place, and tighten it to the roof with nails or screws. Wipe up excess caulking that squeezes out from the edges of the flashing. Replace the roof shingles you lifted, tucking the ends over the underlying vent flashing to encourage proper water run-off.
Source...