Why does my yard smell like a septic tank?
Short answer
A septic smell outside often comes from the plumbing vent, a loose lid or inspection cap, a full tank, or a failing leach field. A working system should have little or no odor. If you also see wet or spongy ground, keep away and call a professional or your local health department, because sewage may be reaching the surface.
A properly working septic system has little or no odor, according to the University of Minnesota. So a smell is worth tracking down, even when the cause turns out to be simple.
Where is the smell strongest?
| Where you notice it | Likely source | What to do |
|---|---|---|
| Near the roof or across the yard | Plumbing vent, carried down by wind | Ask about extending the vent or adding a carbon filter |
| Around the tank | Loose lid, worn seal or full tank | Check that lids look secure, then call a professional |
| Near an inspection pipe | Broken or loose cap | Replace the cap |
| Near a pump tank or treatment unit | Leak or unit problem | Call your service provider |
| Over the leach field | Possible failure | Keep away and call for help |
Why does a roof vent cause yard smells?
Your plumbing releases gas through a vent on the roof. Usually it drifts off. But the University of Minnesota says homes in valleys, forested areas or low spots can have wind patterns that push it back down into the yard. Extending the vent can help. So can a carbon filter, as long as it doesn't block airflow, and it will need replacing.
Could the tank be full?
Yes, and pumping may clear the odor. Check your records, or use our pumping calculator for a rough estimate. Don't count on additives: the same University of Minnesota article says no independent research verifies they work.
When is a septic smell urgent?
Stay safe
Strong odors with wet or spongy soil can mean sewage is reaching the surface, which the University of Minnesota calls an imminent health threat. Keep people and pets away. NDSU Extension advises getting immediate medical care for symptoms such as headache, nausea, dizziness or drowsiness that may come from sewer gas.
Never open a tank to find the smell. Tank gases can kill.
What if the smell is inside?
Indoors, it's usually the plumbing, the University of Minnesota says. A dried-out floor drain trap is a common culprit, so pour water into drains you don't use. A frozen or blocked roof vent can also cause odors and gurgling.
Quick answers
Is it normal to smell a septic tank outside?
An occasional faint smell near the vent can happen, but a working system should have little or no odor. Regular or strong smells need checking.
Who do I call about a septic smell?
The EPA recommends a local septic service provider or plumber.
Sources
- Outdoor septic odor causes and solutions, University of Minnesota Onsite Sewage Treatment Program
- Troubleshooting, University of Minnesota Onsite Sewage Treatment Program
- Care and maintenance, University of Minnesota Onsite Sewage Treatment Program
- Check Your Sewer Vents, NDSU Extension
- Frequent Questions on Septic Systems, US EPA
Read next
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Signs of a failing septic system
Sewage backups, slow drains, wet ground and odors can all point to a septic problem. Learn what each sign may mean and what to do first.
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Septic tank lids and risers explained
A secure septic lid can save a life, and a riser makes pumping easier. Learn what they do, what to check, typical costs and how to stay safe.
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Signs of a clogged leach field and what to do
Slow drains, soggy ground and sewage smells can point to a clogged leach field. See the causes, what to do first and why pumping may not fix it.