How to install bathroom ventilation pipes

July 24, 2019Blog Standard

Vent pipes are connected to the drain lines to allow the waste gases to exit the line. They go from the sewer line through the wall of poles 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 black ABS pipe) and how far to connect the pipe to the drain pipe of the toilet, sink or shower. With these two problems, contact your local permit office to comply with local laws.


  1. Cut into the existing sewer line in the right place with a hacksaw (make two parallel cuts), so that a coupling can be installed. It is a T-shaped coupling that has the same diameter as the sewer line pipe, and a smaller 1 1/2-inch pipe that comes out of its side. The ventilation line grants this coupling. Remove all burrs with a dealer’s knife before applying the glue to the outer ends of the sewer cut line, and inside both ends of the coupling. Attach the coupling to the drain pipe, making sure that the pipe on the side is up and towards the wall of posts, and hold it in place for at least 30 seconds.
  2. Make all the necessary holes in your wall studs to allow the vent line to travel up (and through) the roof. These holes should be 1/2 inch wider than the diameter of the vent pipe, for easy access. Do not make the holes larger than that, as it will weaken the wall studs structurally. Also drill a hole of the same size through the roof.
  3. Connect the new vent line for the drain pipe coupling, glued to the inside of the coupling and the outside of the vent pipe first. Keep together for at least 30 seconds. Continue as fashion, the execution of the ventilation pipe through the wall of poles and the roof, joining pieces together with couplings (you can reach directly, 30, 45, 60 and couplings of 90 degrees) and cut the Ventilation line, where necessary with the hacksaw.
  4. Place a roof shield over the top of the vent pipe, pushing it down so that it rests on the roof. Slide the metal base under the upper tiles. Nail the roof shield under the upper tiles with a hammer and roof nails, but nowhere else (three will suffice). Replace the tiles on each side of the ventilation grille, as well as then, if they are damaged.

Tips and warnings

  • ABS (acrylonitrile butadiene styrene) is a black plastic tube (and couplings) that does not require priming before gluing.
  • If you are using PVC ventilation pipe, first each area before gluing first.
  • A roof shield is a metal plate with rubber in its center that allows the vent pipe to be pushed through the rubber section. This prevents water from getting through the hole in which the ventilation pipe passes through the roof.
  • Consult your local permit office to see how much ventilation should protrude from the ceiling, before cutting the end off.

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