How to Determine the Source of a Sewage Smell

Written by truell bliss
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How to Determine the Source of a Sewage Smell
A sewer drain may not have any odour. (Jupiterimages/ Images)

A sewage smell can spoil a property sale. It can also wreak havoc in the mind of a homeowner who tries to pinpoint the source of the foul odour. An odour of sewage often seems impossible to pinpoint. You detect the smell in places where you would least expect it. Sewage smells can occur indoors, outdoors, upstairs or down, and you should keep searching until you locate the cause. All sewage smells do not indicate a sign of system failure.

Skill level:
Moderately Challenging

Things you need

  • Ladder
  • Garden hose

Show MoreHide


  1. 1

    Walk through the house and let your nose guide you to the odour. Begin the process of elimination with the most common problem, a dry pipe trap. When a toilet, sink, or shower receives little use, the water in the trap evaporates and sewer gas escapes. Operate these conveniences a few times to cure a dry trap.

  2. 2

    Check the vent pipes in the attic. Sometimes a pipe becomes dislodged; storing furniture and other household items can accidentally dislodge a vent pipe and allow sewage odours to accumulate within the home.

  3. 3

    Climb up on the roof and check the vent pipes, the black pipes that rise about 3 feet into the air above the roof. Normally, you find one vent pipe for each toilet in the home. A clogged vent pipe causes sewage odour to permeate the house. Run water into each pipe and wait a minute or two. If the pipe has an obstruction, such as accumulated leaves or a dead animal, water will flow in reverse out of the pipe.

  4. 4

    Walk around the perimeter of the house and check the soil conditions. Mushy soil that rarely dries out indicates a potential malfunction of a septic system or a crack in an exterior sewer line. Sewage odour accompanies each of these conditions and soggy soil attracts flies.

  5. 5

    Check the waste line in the basement of the dwelling. Locate the point at which it enters the basement through the foundation. Any seepage, sewage odour or dampness at or around the point of entry indicates a compromised waste pipe.

Tips and warnings

  • Check to make sure your basement sump pump is working.
  • Certain forms of mould emit noxious odours.

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