How to Vent a Roof for the Septic System

Most homeowners never notice the vents for their septic system until they experience bad smells coming from a sink or toilet. When homes are constructed, builders install septic vents within the walls that emerge either through the roof or through the upper portions of exterior walls. These vents prevent or reduce vapor locks that inhibit sewer drainage. If you’re building a new home or remodeling, you’ll want to vent your plumbing.

Things You'll Need

  • 2-inch PVC pipe (various lengths)
  • PVC adapters
  • PVC glue
  • Hacksaw
  • Vent cover
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Instructions

    • 1

      Check with your local building code before installing the vents. Most vent pipes are approximately 2-inches in diameter but some areas require a different size.

    • 2

      Vent the plumbing in new construction before the framed walls are sheet rocked. Vent piping runs vertically in the stud spaces behind the sink.

    • 3

      Install a 2-inch PVC pipe as a vent just behind the wall where the sink drain enters the stud space. A “T” adapter, made of PVC, attaches to the drainpipe from the sink. The upper side of the “T” attaches to the 2-inch vent pipe, the lower side extends downward to serve as the drain.

    • 4

      Install one vent per bathroom or kitchen. Since the idea behind a vent pipe is to prevent vapor locking, one vent behind the sink provides sufficient venting for the sink, bathtub and toilet if they share a common drain. However, if the plumbing for the fixtures is not connected, an additional vent will be required.

    • 5

      Cut the PVC pipe to fit, clean the end thoroughly and use PVC glue to attach it to the “T” adapter.

    • 6

      Connect the vents in the attic, if possible. To do this, install PVC elbow adapters on the top of the vent pipes as they reach the floor joists in the attic. Use additional vent piping to bring them to a common location and install more adapters until you only have one vent pipe. This pipe will extend upwards through the roof.

    • 7

      Cover the vent pipe on the exterior of the roof with a turbine vent or another decorative vent. Most septic vent pipes emerge in the back of the house where they are less noticeable.

    • 8

      Run separate vent pipes if you have no way of comfortably connecting the pipes in the attic. In this case, you will run two or more vents upwards through the roof but keep in mind that each vent in the roof increases the chance of water leakage.

    • 9

      Use an auto-vent in a remodel where you can’t install a vertical pipe. Although these are less effective, they attach to your drainpipe, in place of the PVC vent and contain a small flapper designed to regulate airflow and reduce the chance of vapor locking or fumes.