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How to Diagnose Building Drains as the Source of Sewage or Septic Odors InspectAPedia®  -     How to identify problems with building drains as the source of sewer gas odors & smells Causes and cures for sewer gas odors related to wet or cold weather How to find and cure bad smells in buildings

This article 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. 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. Citation of this article by reference to this website and brief quotation for the sole purpose of review are permitted.

Use of this information at other websites, in books or pamphlets for sale is reserved 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.

© 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.

Blocked or slow building drains as a sewage gas odor source

A second indoor sewer gas odor explanation is that there may be a partial blockage in a waste line such as between house and septic tank or less likely between septic and fields.

The "glub glub" sound discussed above can also be caused by a partially-blocked drain which is simply slow.

When a building drain is slow due to partial blockage (or bad venting), sewer gases, smells, odors may travel backwards up into the building through the plumbing drain openings.

If the building drain waste vent system has inadequate venting a result may be the loss of water from the building fixture traps. In turn this loss of water from traps permits sewer gases to rise up drain piping and out into occupied space through the building sinks, showers, tubs, and in extreme cases, even toilets.

Dont' forget that a loose toilet may itself be an odor source - with sewer gases leaking out around the toilet base. If sewer gas smells are peculiar to a single bathroom we might check for toilet leaks. Even if a toilet seems bolted securely to the floor, its wax ring seal may be damaged, permiting sewer gases and odors into the building. At Fixture versus system blockage (just below) we provide steps to diagnose plumbing fixtures as the prime odor sources.

Drain noises due to bad venting or due to a partial blockage will be invariant day or night, depending on drain usage, but in the more quiet still and cool night air, drain noises are more easily heard.

As we said earlier, partially blocked building drain, septic tank, or drainfield can generate odors indoors or outside.

Odors in this case will usually correspond to surges in system use, and odors should not correspond particularly to cold weather, except insofar as cold still air may permit gases to fall (from a plumbing vent stack, for example) , or different seasonal wind patterns may cause gases to move to areas where they're not noticed in warmer weather.

See Plumbing Vent Defects for procedures to diagnose problems with the building drain vent system.

See Using the TIF 8800 Gas Detector for tips on using a gas detction instrument to scan for sewer gas sources in a building.

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Use links just below 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.

ANIMAL ODORS IN BUILDINGS
CARBON MONOXIDE & GAS HEAT ODORS
CARPETS & PADDING ODORS IN BUILDINGS
GAS MEASUREMENT TOOLS
MOLD ODORS, Musty Smells in Buildings
OIL HEAT ODORS
OIL TANK LEAK ODORS
PAINTS & COATINGS ODORS IN BUILDINGS
SEPTIC SYSTEMS HOME
SEPTIC INFO ARTICLES
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
HOME BUYERS GUIDE to SEPTIC SYSTEMS
MVOCs & MOLDY MUSTY ODORS
ODORS & SMELLS DIAGNOSIS & CURE
SEPTIC SYSTEMS ONLINE BOOK
SEPTIC TANK PUMPING SCHEDULE
SEPTIC TANK PUMPING PROCEDURE
SEPTIC TANK INSPECTION PROCEDURE
SEPTIC FIELD INSPECTION
SEPTIC TREATMENTS
SEPTIC CONSULTANTS
SEPTIC AUTHORITIES
SEPTIC SYSTEM BOOKS REFS CODES
SEPTIC SYSTEM DESIGN MANUAL - Online
SEPTIC SYSTEM DESIGN BASICS
SEPTIC DESIGN ALTERNATIVES
SEWER LINE REPLACEMENT

• 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.

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

• Our recommended books about building design, inspection, and repair, and about indoor environment testing, diagnosis, and cleanup are at the InspectAPedia Bookstore.
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More Information on Building Diagnostic Inspections and Repairs

• Sewer Gas Odors diagnosing, finding, and curing septic tank and sewer line smells.
• Drain Noises: may indicate defective or clogged plumbing: how to diagnose and cure drain sounds


• The Septic System Information Website Home Page: public information website about septic system design, installation, maintenance, and repair
• Ten Steps to Keeping a Septic System Working, suggestions from the U.S. EPA, edits and additions by DJF
• What is a Septic System An Engineer's View & Septic System FAQ's
• 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.
• Ten Steps to Keeping a Septic System Working, suggestions from the U.S. EPA, edits and additions by DJF
• 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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