How to install a sewer pipe vent

Written by steve sloane
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How to install a sewer pipe vent
Cut through the existing sewer pipe with a hacksaw. (hacksaw image by Aleksandr Ugorenkov from

Sewer lines in homes have vent pipelines attached to them so that gasses can escape the sewer line, as well as allowing fresh air to enter into the sewer line. The vent pipe is joined to the sewer line with a connecting coupling, which (depending on code) is within a certain proximity to the water appliance. The vent pipe travels up through the interior wall cavity and exits through a hole in the roof. It is held in place with a roof shield.

Skill level:

Things you need

  • Tape measure
  • Marker pen
  • Hacksaw
  • Utility knife
  • PVC primer
  • PVC connecting coupling
  • PVC vent pipe
  • PVC couplings
  • PVC cement
  • Power drill
  • 1/2-inch wood drill bit
  • Roof shield
  • 3 roof nails
  • Hammer
  • Eye goggles

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  1. 1

    Mark the existing sewer pipe in the place where the vent pipe will be attached. Make a second mark along the sewer pipe 2 inches from the first mark. Cut right through the sewer pipe at both marks, making the cuts both straight and parallel with each other. Use a hacksaw, handsaw or power saw. Remove any burrs by scraping them off with a utility knife.

  2. 2

    Apply PVC primer around both existing sewer pipe ends and the inside ends of a PVC connecting coupling. Apply PVC cement to the inside ends of the coupling and the outside ends of the cut sewer pipe. Quickly push the coupling between the cut pipe ends, pointing the coupling's side spout up toward the wall cavity. Hold this in place for 10 seconds to allow the cement to dry.

  3. 3

    Prime one end of a section of PVC vent pipe and the inside end of the coupling's side spout. Apply PVC cement to both primed areas. Push the pipe end into the spout. Hold this in place for 10 seconds. Measure, cut and install with primer/cement all the necessary pipe and couplings into the wall cavity, until the pipe reaches the roof. Drill horizontal wall studs (called plates) to create holes for the pipe to pass through. Use a 1/2-inch wood drill bit, and don't make the holes larger than a 2-inch diameter.

  4. 4

    Drill a 2-inch diameter hole through the roof and push a PVC vent pipe through the hole. Cut the pipe 12 inches above the roof level.

  5. 5

    Pull the roof shingles up on the area above the pipe. Slip a roof shield over the top of the pipe and push the pipe through the hole in the central rubber section of the shield, sliding the shield down so that it rests on the roof. Hammer 3 roof nails into the top side of the shield and lower the raised shingles down into place over the nails.

Tips and warnings

  • Do not install nails on the sides or bottom of the shield, as this may cause leaks in the roof.
  • Make sure the hole in the central rubber section of the roof shield accommodates the diameter of vent pipe you are installing.
  • The connecting coupling will be the same diameter as the existing sewer line. Its side spout will be the same diameter as the vent pipe that will be installed.
  • Vent pipe diameters vary depending on local building codes.
  • If installing ABS vent pipe and couplings, use ABS cement but do not use primer.
  • Wear eye protection when cutting the vent pipe.

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