Troubleshooting: What To Do About Odor Complaints

Troubleshooting: What To Do About Odor Complaints
Jim Anderson

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A common call from homeowners involves complaints about odors either inside or outside the house. Odor can be a vexing problem and difficult to track down, so sometimes it’s best to eliminate each possible cause before moving onto the next. 

Inside odors 

Odor inside the house usually indicates a plumbing or vent installation problem. One very common cause associated with the plumbing is an unused sink or floor drain. Over time water in the trap dries up and the system ends up venting through the drain. 

This often happens in homes where a basement has been finished off into rooms or the laundry facilities have been moved. It can be difficult to locate these drains because they have been covered up or hidden. A conversation with the homeowner about recent work done in the house is an important part of troubleshooting. 

Another related cause for odor problems from dried out taps involves a sump pump in the lowest level of the house that pumps raw sewage up into the house sewer and out to the septic tank. Frost can form in the vent during cold weather, effectively preventing gases from venting. 

When the sump is full and the pump starts running a vacuum is formed and the water in the traps is sucked out allowing gases and odors to vent through the plumbing. In this case the homeowner will need to be vigilant about keeping the roof vent open during the winter. Of course, other things can plug the vent, such as birds, insects or animals, so it’s not solely a problem in cold climates. 

During nice weather, make sure odors are not actually coming from outside through an open window. 

Outside odors 

If the odors are outside, there are a couple of typical causes. With maintenance in mind during septic tank installation, it is recommended that risers be brought to the surface to provide easier access. If the lids are not properly sealed there can be a slight air gap, and when the wind blows over the top of the lid and risers the odors can be pulled out of the tank. 

The solution here is to make sure the lids are tightly sealed with no air gaps. For older lids this may require completely replacing the lid, replacing the rubber seal, or adding weather stripping to the lid. Do not use a material that actually glues or seals the lid shut; the risers are there so maintenance can be performed. 

Roof vent placement 

Another common cause of odors is the height and placement of the house roof vent relative to tall trees, and the pitch of the roof or the setting of the house relative to the topography. Homeowners smell odors only when the wind is blowing from a certain direction because air currents around the vent cause the odors to fall to the ground rather than rise and dissipate. 

Solutions include extending the vent pipe so it is higher relative to the roof pitch or installing a carbon filter. Be aware that in cold climates this can create frost-plugging problems and the filter will need to be changed.

As always, good communication with the homeowner is the key to successfully resolving these problems. 

About the Author
Jim Anderson is connected with the University of Minnesota onsite wastewater treatment education program, is an emeritus professor in the university’s Department of Soil Water and Climate, and education coordinator for the National Association of Wastewater Technicians. Post a comment below or send him questions about septic system maintenance and operation by email to


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