How to Diagnose and Eliminate Cold-Weather-Related Sewer Gas Odors InspectAPedia® -
How to diagnose plumbing drain traps or plumbing drain siphonage as a source of sewer smells and odors
How to diagnose cold or freezing weather as a cause of septic odors indoors
Causes and cures for sewer gas odors related to wet or cold weather
Questions & answers about troubleshooting and fixing septic or sewer odors in and around buildings when the odors appear mostly in wet or cold weather.
Cold weather sewer or septic odor troubleshooting: this article series discusses the diagnosis and correction of sewer gas or septic odors (and other building smells and odors with focus on diagnosing odor sources and causes in cold weather.
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Some of the diagnostic steps pertain to all seasons. Also see ODORS & SMELLS DIAGNOSIS & CURE for procedures to diagnose and cure all kinds of odors in and around buildings.
Also see our broad-scope article on diagnosis and cure of sewer gas and septic odors: Sewer Gas Odors diagnosing, finding, and curing septic tank and sewer line smells.
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to the author. Technical reviewers are welcome and are listed at "References."
This is a chapter of Inspecting, Testing, & Maintaining Residential Septic Systems an online book on septic systems.
Smelling sewage odors inside only, or mostly inside
Here are some places to look and perhaps to fix if you're smelling sewage or septic like odors inside of a building:
All drains and traps may smell and produce a little methane gas: Beware of mistaking normal drain odors, or gases detected with very sensitive instrumentation for an abnormal condition or a problem. A little gas odor is detectable at many fixture drains and traps since there is likely to be decaying organic matter there. Check for dry plumbing traps. If the trap is dry and odors are present, that's a problem and we'll need to determine why the trap was dry: from dis-use and evaporation, from siphonage, or some other fault such as a rusted through or leaky trap itself.
Blocked or Inadequate Plumbing Vents can cause odor backdrafting into a building. See Plumbing Vent Defects for diagnostic details.
Dry Plumbing Traps can serve as a Sewer Gas Odor Source indoors - check all of your fixtures, especially ones which have not been used in some time
or ones which are lacking proper venting. A plumbing trap serving an unused sink or shower or tub can dry out and permit sewer gases to enter the building up through the fixture. See TRAPS on DRAINS for diagnostic details.
Fixtures which are not properly vented may lose their water trap: If the fixture is not properly vented, even if it's in-use, the water that is supposed to be in the fixture trap may be siphoned away, permitting sewer gases to enter the building. See Plumbing Vent Defects for diagnostic details.
Plumbing vents as an odor source: a leaky plumbing vent could be an odor source indoors. The odor may not be coming from plumbing drains: If none of the building drains are clogged or slow and if the septic system is otherwise working one's first guess would be a problem with the plumbing the vent system. This condition can occur year round. See Plumbing Vent Defects for diagnostic details.
You can usually spot inadequate or blocked plumbing venting by noticing, for example, that tub, shower, or sink drain makes a gurgling or "glub glub" sound when a nearby toilet is flushed or when a full fixture is being drained. Inadequate or blocked plumbing venting can also mean that a plumbing fixture does not drain well (even though the drain line is not blocked).
Inadequate venting produces a glub glub sound as water passes down a drain and cannot draw air in after itself through a plumbing vent stack.
Instead the drain has to draw air in to itself through various plumbing traps which, as they normally contain water, produces the glub glub sound as air passes through the trap. This defect can siphon water out of traps and let sewer gases back into a home - smelly and potentially dangerous (methane gas).
Also see Drain Noises: may indicate defective or clogged plumbing: how to diagnose and cure drain sounds
Cold Weather and Plumbing Vent Blockage Problems as a Source of Building Smells, Septic or Sewage Odors
What's different in cold weather that could cause indoor sewer gas odors only during freezing weather?
An under-sized plumbing vent (less than 2" diameter or too short above the roof line) can become blocked by frost in the vent line above the roof, blocked by snow cover, or have its gases blown down to a lower level by cold or varying air movement. If it's a plumbing vent diameter problem in a freezing climate, you'll see the vent basically blocked by frost above the roof line.
Too-short plumbing vents: Look also for short plumbing vent stacks above the roof line - they can be covered and blocked by snow.
If in cold weather a plumbing vent pipe is frosting up, sewer gases may vent backwards out through building drains. In that case, even re-priming building drain traps won't prevent sewer gas entry as flushing a toilet or running a nearby drain can siphon water out of a nearby trap.
A thoughtful reader, Jill Elwert, suggested insulating the vent piping to try to delay vent pipe blockage by freezing moisture. We are afraid that even if you insulate the vent line in a cold attic, it'll freeze above the roof surface outdoors. You could try it but if that proves the problem, ultimately you'll want to have a plumber or handyman install a 2" or larger diameter vent from the attic floor up through the roof. See Remedies for Sewer Odors.
Diagnosing frozen plumbing vent lines:
Noisy drains only in freezing weather: Look for a clue of blocked vents (from freezing moisture) by listening for a glub glub sound at nearby drains, say when flushing a toilet or emptying a bathtub.
Poor drainage only in freezing weather: Another blocked vent line symptom might be poor drainage that occurs only in freezing weather.
Rooftop inspection for frozen or snow-covered plumbing vents: WATCH OUT! don't try going on an icy, wet, high, steep, or snow-covered roof. But if the roof is safely accessible, or you can get visual access, perhaps from a higher elevation, or some safe location with binoculars, see if you see frost build-up in the plumbing vent.
Priming the plumbing trap (where sewage odors are most observed) by pouring water into it may stop the sewer gas odor, but if the plumbing vent is blocked, the trap is likely to lose its prime and the odors will return.
Inspect for small diameter plumbing vents above the roof line or in the attic - just a simple visual inspection can tell you where to look first for frozen, blocked plumbing vents. Start with the smallest diameter vents, especially if the plumbing vent is one that vents a place where lots of hot (steamy) water is run such as a vent for a clothes washer, kitchen sink, or shower.
Plumbing Vent Problems and Trap Siphonage, Dry Plumbing Traps and Sewer Gases
Freezing weather can cause a complete blockage of a plumbing vent stack by frost. For example steam from long showers moves up the vent pipe where it freezes in the pipe section extending above the building roof.
The absence of venting (missing or blocked) causes plumbing trap siphonage and loss of water in building traps. (Water flowing down a drain line without a nearby supply of makeup air to follow the water creates a vacuum that pulls water out of nearby plumbing traps. Flushing a toilet can siphon out a nearby sink or tub trap.)
What happens when the water seal is lost from a plumbing trap?
When the water seal is lost from a plumbing trap sewer gases can back up out of that fixture and not just smell bad. Sewer gases contain methane which is an explosive gas - possibly quite dangerous. In addition to occasional methane gas explosions inside buildings, I've had a report of an outdoor septic tank explosion too when an owner built a brush fire atop the tank.
In sum, dry plumbing traps are caused by evaporation at an unused fixture, leaks at the trap, or siphonage due to improper plumbing vent line installation. Dry traps can leak smelly or dangerous sewer gases into a building.
Check for dry plumbing traps, particularly at un-used basement or lower floor fixtures and at floor drains which might be connected to the sewer line. "Dry trap" means that there is no water in the trap bend or weir.
Questions & answers about troubleshooting and fixing septic or sewer odors in and around buildings when the odors appear mostly in wet or cold weather.
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Herb Reed County Extension Director, Agricultural and Natural Resources Educator, Calvert County Maryland - private email to DF 9/5/2006 adding comments about odors and partial blockages.
Thanks to reader Jill Elwert for discussing sewer gases that occur in cold or freezing weather, 12/08/2009
Septic Tank Capacity vs Usage in Daily Gallons of Wastewater Flow, calculating required septic tank size, calculating septic tank volume from size measurements
Septic Tank/Soil-Absorption Systems: How to Operate & Maintain [ copy on file as /septic/Septic_Operation_USDA.pdf ] - , Equipment Tips, U.S. Department of Agriculture, 8271 1302, 7100 Engineering, 2300 Recreation, September 1982, web search 08/28/2010, original source: http://www.fs.fed.us/t-d/pubs/pdfimage/82711302.pdf.
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.)
...
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
Advanced Onsite Wastewater Systems Technologies, Anish R. Jantrania, Mark A. Gross. Anish Jantrania, Ph.D., P.E., M.B.A., is a Consulting Engineer, in Mechanicsville VA, 804-550-0389
(2006), Advanced Onsite Wastewater Systems Technologies.
Outstanding technical reference especially on alternative septic system design alternatives. Written for designers and engineers, this book is not at all easy going
for homeowners but is a text we recommend for professionals--DF.
AEROBIC SEPTIC SYSTEMS
Builder's Guide to Wells and Septic Systems, Woodson, R. Dodge: $ 24.95; MCGRAW HILL B; TP;
Quoting from Amazon's description: For the homebuilder, one mistake in estimating or installing wells and septic systems can cost thousands of dollars. This comprehensive guide filled with case studies can prevent that. Master plumber R. Dodge Woodson packs this reader-friendly guide with guidance and information, including details on new techniques and materials that can economize and expedite jobs and advice on how to avoid mistakes in both estimating and construction. Chapters cover virtually every aspect of wells and septic systems, including on-site evaluations; site limitations; bidding; soil studies, septic designs, and code-related issues; drilled and dug wells, gravel and pipe, chamber-type, and gravity septic systems; pump stations; common problems with well installation; and remedies for poor septic situations. Woodson also discusses ways to increase profits by avoiding cost overruns.
Country Plumbing: Living with a Septic System, Hartigan, Gerry: $ 9.95; ALAN C HOOD & TP;
Quoting an Amazon reviewer's comment, with which we agree--DF:This book is informative as far as it goes and might be most useful for someone with an older system. But it was written in the early 1980s. A lot has changed since then. In particular, the book doesn't cover any of the newer systems that are used more and more nowadays in some parts of the country -- sand mounds, aeration systems, lagoons, etc.
Design Manuals for Septic Systems
US EPA Onsite Wastewater Treatment Systems Manual [online copy, free] Top Reference: US EPA's Design Manual for Onsite Wastewater Treatment and Disposal, 1980, available from the US EPA, the US GPO Superintendent of Documents (Pueblo CO), and from the National Small Flows Clearinghouse. Original source http://www.epa.gov/ORD/NRMRL/Pubs/625R00008/625R00008.htm Onsite wastewater treatment and disposal systems,
Richard J Otis, published by the US EPA. Although it's more than 20 years old, this book remains a useful reference for septic system designers.
U.S. Environmental Protection Agency, Office of Water Program Operations; Office of Research and Development, Municipal Environmental Research Laboratory; (1980)
"International Private Sewage Disposal Code," 1995, BOCA-708-799-2300, ICBO-310-699-0541, SBCCI 205-591-1853, available from those code associations.
"Manual of Policy, Procedures, and Guidelines for Onsite Sewage Systems," Ontario Reg. 374/81, Part VII of the Environmental
Protection Act (Canada), ISBN 0-7743-7303-2, Ministry of the Environment,135 St. Clair Ave. West, Toronto Ontario M4V 1P5 Canada $24. CDN.
Manual of Septic Tank Practice, US Public Health Service's 1959.
Onsite Wastewater Disposal Books
Onsite Wastewater Disposal, R. J. Perkins;
Quoting from Amazon: This practical book, co-published with the National Environmental Health Association,
describes the step-by-step procedures needed to avoid common pitfalls in septic system technology.
Valuable in matching the septic system to the site-specific conditions, this useful book will help you install a reliable system in
both suitable and difficult environments. Septic tank installers, planners, state and local regulators, civil and sanitary engineers,
consulting engineers, architects, homeowners, academics, and land developers will find this publication valuable.
Onsite Wastewater Treatment Systems, Bennette D. Burks, Mary Margaret Minnis, Hogarth House 1994 - one of the best septic system books around, suffering a bit from small fonts and a weak index. While it contains some material more technical than needed by homeowners, Burks/Minnis book on onsite wastewater treatment systems a very useful reference for both property owners and septic system designers.
Septic Tank/Soil-Absorption Systems: How to Operate & Maintain [ copy on file as /septic/Septic_Operation_USDA.pdf ] - , Equipment Tips, U.S. Department of Agriculture, 8271 1302, 7100 Engineering, 2300 Recreation, September 1982, web search 08/28/2010, original source: http://www.fs.fed.us/t-d/pubs/pdfimage/82711302.pdf
Planting Over Septic System Component", Daniel Friedman (author/editor, InspectAPedia.com), The Innovator, Winter/Spring 2008, BCOSSA, British Columbia OnSite Sewage Association, 201-3542 Blansard St., Victoria BC V8X 1W3 Canada
Septic System Owner's Manual, Lloyd Kahn, Blair Allen, Julie Jones, Shelter Publications, 2000 $14.95 U.S. - easy to understand, well illustrated, one of the best practical references around on septic design basics including some advanced systems; a little short on safety and maintenance. Both new and used (low priced copies are available, and we think the authors are working on an updated edition--DF.
Quoting from one of several Amazon reviews: The basics of septic systems, from underground systems and failures to what the owner can do to promote and maintain a healthy system, is revealed in an excellent guide essential for any who reside on a septic system. Rural residents receive a primer on not only the basics; but how to conduct period inspections and what to do when things go wrong. History also figures into the fine coverage.
Test Pit Preparation for Onsite Sewage Evaluations, State of Oregon Department of Environmental Quality, Portland OR, 800 452-4011. PDF document. We recommend this excellent document that offers detail about soil perc tests, deep hole tests, safety, and septic design. Readers should also see Soil Percolation Tests and for testing an existing septic system, also see Dye Tests
Grass is Always Greener Over the Septic Tank, Bombeck, Erma: $ 5.99; FAWCETT; MM;
This septic system classic whose title helps avoid intimidating readers new to septic systems, is available new or used at very low prices.
It's more entertainment than a serious "how to" book on septic systems design, maintenance, or repair. Not recommended -- DF.
US EPA Onsite Wastewater Treatment Systems Manual Top Reference: US EPA's Design Manual for Onsite Wastewater Treatment and Disposal, 1980, available from the US EPA, the US GPO Superintendent of Documents (Pueblo CO), and from the National Small Flows Clearinghouse. Original source http://www.epa.gov/ORD/NRMRL/Pubs/625R00008/625R00008.htm
Water Wells and Septic Systems Handbook, R. Dodge Woodson. This book is in the upper price range, but is worth the cost for serious septic installers and designers.
Quoting Amazon: Each year, thousands upon thousands of Americans install water wells and septic systems on their properties. But with a maze of codes governing their use along with a host of design requirements that ensure their functionality where can someone turn for comprehensive, one-stop guidance? Enter the Water Wells and Septic Systems Handbook from McGraw-Hill. Written in language any property owner can understand yet detailed enough for professionals and technical students this easy-to-use volume delivers the latest techniques and code requirements for designing, building, rehabilitating, and maintaining private water wells and septic systems. Bolstered by a wealth of informative charts, tables, and illustrations, this book delivers: * Current construction, maintenance, and repair methods
* New International Private Sewage Disposal Code
* Up-to-date standards from the American Water Works Association
Wells and Septic Systems, Alth, Max and Charlet, Rev. by S. Blackwell Duncan, $ 18.95; Tab Books 1992. We have found this text very useful for conventional well and septic systems design and maintenance --DF.
Quoting an Amazon description:Here's all the information you need to build a well or septic system yourself - and save a lot of time, money, and frustration. S. Blackwell Duncan has thoroughly revised and updated this second edition of Wells and Septic Systems to conform to current codes and requirements. He also has expanded this national bestseller to include new material on well and septic installation, water storage and distribution, water treatment, ecological considerations, and septic systems for problem building sites.
The NSFC Products List has an excellent list of design manuals/modules available from their website or by telephone 800-624-8301
Submissions welcome. send us a suggested document link or request an exchange of website links
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