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How to Track the Source of Sewer Gas Smells and Septic Tank Odors InspectAPedia®  -

How to track septic odors or sewer gas odors to their source What diagnostic questions to ask when finding the source of a septic or sewer gas smell 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

This page describes how to track down the source of septic or sewer gases as a step in the procedure to diagnose, find, and cure odors in buildings including septic or sewage 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 Wet Weather or Cold Weather Septic Odors or Sewage Odor Diagnosis & Repair Guide for additional odor tracing and cure advice for odors occurring during wet or cold weather.

© Copyright 2009 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

Guide to Tracking Sewer Odors to Their Source

Before proceeding to the more detailed septic odor diagnostic articles listed below, see if you or other friends and family members can make these simple diagnostic observations. Each of these answers can point to some of the specific odor causes we list in our detailed articles below. Don't worry if you don't know the answer, just collect what data you can and then proceed to the detailed articles we list below.

1. Where is the sewer or septic smell strongest? Indoors, or outdoors?
   1. Indoors odor tracking: on what floor of the building and in what room(s) is the odor strongest? This may lead to a specific drain, trap, plumbing fixture, or similar problem
   2. Outdoors odor tracking: on what side of the building is the odor strongest? Does the odor get stronger if you walk away from the building or towards it? Is the odor coming from your property, a storm drain, a neighbor's property?
2. How does the septic or sewer gas odor strength vary? Is the variation associated with:
   1. Weather conditions: sun, sun shining on certain sides of the building or property; rain, freezing weather, snow cover, wind direction.
   2. Time of day: odors may be associated with periods of plumbing system usage; also temperature and wind conditions vary by time of day.
   3. Season of the year: snow cover and freezing weather can make odors appear or disappear.
3. What plumbing or flooding or other events have happened that may relate to odors: such as septic flooding during area flooding, a burst sewer pipe, a sewage leak in a crawl space that was not cleaned up, a change, addition, modification, or repair of the septic system, sewer line piping, or other mechanical systems in the home.
4. Does the building water supply smell funny? Hot water and cold water both or just hot water?
5. When did someone first notice the septic odor or sewer gas odor? and How old is the building?
   1. Has the odor always been present or has it developed recently.
   2. What else happened? If the sewer gas or septic odor began recently, what changes in the building or events at the property can be placed at about the same time as when odors were first noticed? Have there activities such as remodeling, demolition, or plumbing repairs that may have disturbed or affected the building drain waste vent piping, chimneys, gas appliances, or use of chemicals? Dead animals?

The answers to these questions will help you make sense out of the diagnostic suggestions in the articles that follow. Contact Us if you have other diagnostic suggestions or if you simply cannot figure out the source of a problem odor at a building.

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Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

MVOCs & MOLDY MUSTY ODORS
ODORS & SMELLS DIAGNOSIS & CURE
PLUMBING TOPICS
GAS MEASUREMENT TOOLS
SEPTIC SYSTEMS HOME
SEPTIC SYSTEMS ONLINE BOOK
SEPTIC SYSTEM DESIGN BASICS
SEPTIC DESIGN ALTERNATIVES
SEPTIC INSPECTIONS
SEPTIC & CESSPOOL SAFETY
SEWER GAS ODORS
  First Steps for Sewer Gas Odors
  Dangerous Conditions
  Building Drain & Sewer Line Odors
  Cure Odors in Septic Systems
  Other Causes of Odors from a Septic System
  Plumbing Fixtures or Traps
  Plumbing Vent Definitions, Types
  Plumbing Vent Defects
  Septic System or Sewer Piping
  Site, Weather, or Failing Neighbors
  Tests for Indoor Sewer Gas
  Tracking Odors to Source
SEWER GAS ODORS in COLD WEATHER
  Short Answer in Cold Weather
  Diagnosing Sewer Odors
  Cold Weather Plumbing Vent Blockage
  Trap Siphonage and Sewer Gases
  Building drain odor source
  Fixture versus system blockage
  Odors in Wet Weather
  Indoor Septic Odors Outdoor Causes
  Outdoor Odor Sources
  Sewer Odor Tracking
  Remedies for Sewer Odors
  Odors and Drain Lines
  Failed Drainfields and Odors
Toxic Gas Test Procedures

• 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

More Information on Building Diagnostic Inspections and Repairs

• Cold Weather Septic Odors or Sewage Odor Diagnosis for additional odor tracing and cure advice focused on sewer gas odor tracking in cold or wet weather.
• Drain Noises: may indicate defective or clogged plumbing: how to diagnose and cure drain sounds


• The Septic System Information Website home page for this topic
• Septic Systems Inspection, Testing, & Maintenance- online textbook. Detailed how to inspect, maintain, repair information
• The Home Buyer's Guide to Septic Systems
• Septic Tank Pumping Guide: When, Why, How to pump the septic tank
• Home & Outdoor Living Water Requirements
• Septic Tank Capacity vs Usage in Daily Gallons of Wastewater Flow, calculating required septic tank size, calculating septic tank volume from size measurements
• How Big Should the Leach Field Be? - table of soil percolation rate vs. field size
• Septic System Drainfield Absorption System Biomat Formation - what leads to drain field clogging and expensive drainfield repairs
• Table of Required Septic & Well Clearances: Distances Between Septic System & Wells, Streams, Trees, etc.
• 
  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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