How to Install Bathroom Vent Pipes

Vent pipes are connected to sewer lines to allow waste gas to escape from the line.

Vent pipes release gas from the sewer line.Vent pipes release gas from the sewer line.
They go from the sewer line up through the stud wall and out either through the wall of the house, or more commonly through the roof. Two things to consider are the size of the pipe (usually 1 1/2-inch diameter ABS black pipe) and how far to connect the vent to the sewer line from the toilet, sink or shower. With both these issues, contact your local permit office so that you comply with local laws.

Cut into the existing sewer line in the appropriate place with a hacksaw (make two parallel cuts) so that you can install a coupling. This is a T-shaped coupling that has the same diameter as your sewer line pipe, and a smaller 1 1/2-inch pipe coming out of its side. The vent line attaches to this coupling. Remove all burrs with a tradesman's knife before applying glue to both outside ends of the cut sewer line, and the inside both ends of the coupling. Attach the coupling to the sewer line, making sure the side pipe faces up and toward the stud wall, and hold it in position for at least 30 seconds.

Drill all necessary holes in your stud wall to allow the vent line to travel up to (and through) the roof. These holes should be 1/2 inch wider in diameter than the vent line, to give it easy access. Don't make the holes bigger than that, as it will weaken the stud wall structurally. Also drill a same-sized hole through the roof.

Connect the new vent line to the sewer line coupling, gluing the inside of the coupling and outside of the vent pipe first. Hold together for at least 30 seconds. Continue in like fashion, running the vent pipe up through the stud wall and through the roof, joining pieces together with couplings (you can get straight, 30-, 45-, 60- and 90-degree couplings) and cutting the vent line where necessary with the hacksaw.

Place a roof shield over top of the vent pipe, pushing it down so it rests on the roof. Slip the metal base under the top shingles. Nail the shield to the roof under the top shingles with a hammer and roof nails, but nowhere else (three will suffice). Replace shingles on either side of the vent, as well as below, if they are damaged.

Things You Will Need

  • ABS vent pipe
  • ABS couplings (straight, 30-, 45-, 60-, 90-degree)
  • ABS glue
  • Hacksaw
  • Tape measure
  • Pencil
  • Tradesman's knife
  • Roof shield
  • Roof nails
  • Drill
  • Hammer

Tips

  • ABS (acrylonitrile butadiene styrene) is black plastic pipe (and couplings) that requires no primer before gluing.
  • If you are using PVC vent pipe, prime each area first before gluing.
  • A roof shield is a metal plate with rubber in its center that allows for the vent pipe to be pushed through the rubber section. This stops any water getting through the hole where the vent pipe goes through the roof.
  • Consult your local permit office to see how much vent should stick out of the roof, before cutting the end off.

About the Author

Steve Sloane started working as a freelance writer in 2007. He has written articles for various websites, using more than a decade of DIY experience to cover mostly construction-related topics. He also writes movie reviews for Inland SoCal. Sloane holds a Bachelor of Arts in creative writing and film theory from the University of California, Riverside.