Indoor and Outdoor Odors

Some people experience sewer gas odors, either inside or outside a house served by a septic system.  Your tank produces several gases: some odorless, like methane; and others highly noticeable, such as hydrogen sulfide. 

Odors Inside the House:  These odors are usually caused by a trap not being sealed.  Every fixture in the house - including floor drains, tub drains, sink drains and shower stall drains - has a P-trap beneath it which is sealed with water and prevents gases produced in the septic tank from entering the house. If a fixture remains unused over several months, the water in the trap can evaporate, allowing gas to enter the house.  Therefore the most probable culprit of an indoor odor is an under-utilized fixture, such as a floor drain in a basement or utility room ­-or tubs, sinks and showers in an infrequently used extra bathroom.  Drying out of a P-trap occurs more frequently in the winter when the air is dry, and also after a very windy period.  The simple fix is to pour about one quart of water in each drain to re-seal it.

Odors outside the house:  These odors are usually caused by those same tank gases venting through the roof vents of your plumbing system. On a day with a slight breeze, the gas can be pulled down to a deck or patio area, or into an open window, by the vacuum created on the lee side of the house.  This problem can be solved by extending the offending vent pipes above the roof line, or installing one-way check valves - permitting air to enter but not to escape the vent.