How to Vent Sewer Gases


Sewer gas is composed of toxic and non-toxic gases produced due to the decay of household and industrial waste. The gasses can contain methane, carbon dioxide, sulfur dioxide, nitrous oxide, bleaches and ammonia. Traps built into your piping system keep the gasses from coming back into your home through drains or other disposal regions. But the piping system must also be vented to ensure the safety of the air in your home.

Things You'll Need

  • T-connectors
  • Pipe (usually large-mouth PVC)
  • Measuring tape
  • Pipe cutter or saw
  • Vent
  • Rotating fan (optional)
  • Look at your full piping schematic. Plan a centralized area where a majority of your drainage pipes pass. This lets you connect the venting pipes together simply. As water drains with gravity, you should be able to find a drainage area that is fairly central.

  • Attach a T-shape connector to every pipe in your home that drains water. If you are installing new pipe, this provides a straight pass through for the water while letting you attach a pipe upwards for venting gas. If you are using existing pipes, cut the pipe to place the “T” connector and the venting pipe.

  • Connect the pipes to all three sides of the “T,” making sure the venting pipe is vertical. This allows the water to pass by without going into the venting pipe. It also lets the gas escape through the pipe.

  • Seal all three sides of the “T” with waterproof caulk. Make sure the seal is completely secure so you will not have any leaks.

  • Join the venting pipes together with various connectors. You can use “T,” elbow and octopus connectors to get all the pipes heading in the same direction. Each connector should keep building upward so the gas will rise through the pipes.

  • Measure the distance from the connector to the roof of your home. Cut your large-mouth PVC pipe to that length plus an additional six inches. This covers the amount of pipe that will sink into the connector and go out through the hole in your roof.

  • Connect your large mouth pipe to the connected drainpipes and run it all the way to the roof of your house and out the top. There should be a hole provided. If not, you can cut one yourself.

  • Seal the roof around the hole and choose a vent to put on the top. This keeps water from coming in the pipe but lets gas escape. Use a rotating blade fan to add extra protection. This sucks the gas out of the roof.

Tips & Warnings

  • Most drainage pipes converge on one location. If you follow the pipes you should be able to complete the gas vent with only one or two additional pipes. This makes connecting the pieces fairly easy.
  • If you are new to this type of work, consider consulting a professional about the roof portion of the venting system. You want to make sure the gas fully escapes your home and that you are protected from a roof leak.


  • Photo Credit Zedcor Wholly Owned/ Images
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