How to diagnose septic or sewer odors coming from building drain piping
How to prevent or cure sewer gas odors from septic systems, building plumbing, & other causes
Sewer gas smell diagnosis - plumbing checklist
Septic gas smell diagnosis - septic system checklist
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This page describes how to diagnose, find, and cure odors in buildings caused by leaks or other defects in the building drains or sewer line - leaks that make sewage smells or sewer gas smells or "gas odors" in buildings
with a focus on homes with a private onsite septic tank but including tips for owners whose home is connected to a sewer system as well. What makes the smell in sewer gas? Sewer gases are more than an obnoxious odor.
Because sewer gas contains
methane gas (CH4) there is a risk of an explosion hazard or even fatal asphyxiation.
Sewer gases also probably contain hydrogen sulfide gas (H2S) In addition some writers opine that there are possible
health hazards from sewer gas exposure, such as a bacterial infection of the sinuses (which can occur due to any sinus irritation).
Depending on the sewer gas source and other factors such as humidity and building
and weather conditions, mold spores may also be present in sewer gases. Also see CLOGGED DRAIN DIAGNOSIS, Drain Noises (gurgling drains means bad vent piping or clogged drains).
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Building Drain & Sewer Line Defects Can Release Sewer Gases & Odors Indoors
Check for a cap left off of a sewer line cleanout:
Our client is pointing out an open sewer line in the basement of a home she was purchasing. The cap had been left off of a cleanout port where main waste line exited the building.
We suspected more trouble than just an open drain cleanout permitting sewer gases to leak into the basement.
Because this "work" appeared to have just been performed, right before our property inspection, we wondered if someone had been asked to attempt to clear a blocked connection between the building sewer line and the community sewer (or private septic system).
Inspect the building drains and gas lines for leaks: Plumbing drains and traps may smell regardless, as they are usually a reservoir for organic debris.
Remember that a building drain can be leaking inside of a wall or ceiling cavity without showing up as a wet spot or mold.
But if you notice a sewer gas smell particularly at one or more plumbing drains, the fixture may not be properly vented.
If the plumbing fixture or drain "gurgles" or makes funny noises when it is draining, or if you hear gurgling noises at some fixtures, say a sink or tub when nearby fixtures are draining, we would certainly suspect that the fixture is not well vented or may not be vented at all.
If you suspect that odors are due to a problem with the building drains but you cannot find a drain line leak nor an open drain cleanout cover, take a look at CLOGGED DRAIN DIAGNOSIS.
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Thanks to Slade Franklin
for the reminder that a leaky wax ring at a toilet can lead to septic odors in bathrooms. 11/2007
Thanks to J.V. (privacy protected) for the reminder to make a detailed inspection of the plumbing vent system when sewer gas odors are present. 07/2008
Thanks to Roger Hankey & Cheryll Brown, www.hankeyandbrown.com, ASHI home inspectors in Minnesota, for the deteriorated transite pipe gas flue vent photograph and comments. Mr. Hankey is a past chairman of the ASHI Technical Committee, serves as co-chairman of ASHI legislative committee, and has served in other ASHI professional and leadership roles. 7/2007
Septic Tank Capacity vs Usage in Daily Gallons of Wastewater Flow, calculating required septic tank size, calculating septic tank volume from size measurements
What is a Septic System An Engineer's View - Types of treatment tanks, adsorption systems, pumps, and other special equipment are discussed in some further detail in this text
Components of a Septic System- the Basic Parts of a Conventional Septic Tank and Leachfield, a chapter in the Home Buyers Guide to Septic Systems
A Toxic Gas Testing Sampling Plan for Residential Indoor Air Investigations
Pennsylvania State Fact Sheets relating to domestic wastewater treatment systems include
Pennsylvania State Wastewater Treatment Fact Sheet SW-161, Septic System Failure: Diagnosis and Treatment
Pennsylvania State Wastewater Treatment Fact Sheet SW-162, The Soil Media and the Percolation Test
Pennsylvania State Wastewater Treatment Fact Sheet SW-l64, Mound Systems for Wastewater Treatment
Pennsylvania State Wastewater Treatment Fact Sheet SW-165, Septic Tank-Soil Absorption Systems
Document Sources used for this web page include but are not limited to: Agricultural Fact Sheet #SW-161 "Septic Tank Pumping," by Paul D. Robillard and Kelli S. Martin. Penn State College of Agriculture - Cooperative Extension, edited and annotated by Dan Friedman (Thanks: to Bob Mackey for proofreading the original source material.)
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