Photograph of sewer line break in a crawl space How to Track the Source of Sewer Gas Smells and Septic Tank Odors

  • TRACK SEPTIC ODORS to SOURCE - CONTENTS: 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
  • POST a QUESTION or READ FAQs about septic smells or sewer gas smells
InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

How to find and fix septic tank or sewer odors:

This septic odor track-down article 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.

Green links show where you are. © Copyright 2017, All Rights Reserved.

Guide to Tracking Sewer Odors to Their Source

Leaky cast iron building drain proven by septic dye (C) D FriedmanWhat makes the smell in sewer gas? Sewer gases are more than an obnoxious odor.

Watch out: 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.

Track the septic odor strength to a source: The photo shows how this pays off. A family room over this crawl space had the strongest septic odors. An abandoned waste line was no longer connected to a bathroom but it had been left open in the crawl space, permitting gases from the septic system to enter that area.

Is the sewage odor stronger outside or indoors? If indoors, is the odor only at a specific bathroom or fixture? Perhaps there is simply a particular bathroom which is missing a plumbing vent.

If the sewage odor is strongest outside that suggests a septic or sewer gas problem in the septic or sewer system, but don't rule out unusual site or wind conditions discussed below. Track the septic or sewer odor source to its strongest point. Before tearing up your own property or drains or building, let's be sure the odor is coming from your property and not from a neighbor or other facility.

Before proceeding to the more detailed septic odor diagnostic articles listed at the top of this article, 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?

Your answers to these questions will help you make sense out of the diagnostic suggestions in the septic or sewage odor diagnosis & repair articles that are listed below at More Reading.

Also see Sewer Odor Tracking for more site and weather factors in locating the source of a sewer gas smell.

And 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.

Contact Us if you have other diagnostic suggestions or if you simply cannot figure out the source of a problem odor at a building.


Continue reading at TRACK SEWER ODOR by WEATHER or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.



Or see SEWER GAS ODORS - home

Suggested citation for this web page

TRACK SEPTIC ODORS to SOURCE at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia


Frequently Asked Questions (FAQs)

Click to Show or Hide FAQs

Ask a Question or Search InspectApedia

Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.

Search the InspectApedia website

Comment Box is loading comments...

Technical Reviewers & References

Click to Show or Hide Citations & References

Publisher's Google+ Page by Daniel Friedman