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Wet Weather or Cold Weather Sewage or Septic Odors: Diagnosis and Repair Guide InspectAPedia®  -     How to diagnose sewer odors in wet or cold weather 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. The photograph provides a lot of septic odor diagnostic information if you look closely: there is a home made septic tank nearly touching the building wall (by those steps), and in the foreground is a pony pump that the owner was using to try to move septic effluent uphill to his drainfield. This system would not work reliably: the tank is too small for normal use and the pump is exposed to freezing.

Also see ODORS & SMELLS DIAGNOSIS & CURE for procedures to diagnose and cure all kinds of odors in and around buildings.

Odors from the septic tank were strongest at the front entry door to the home, perhaps in part because the system was in failure and backing up. This article on diagnosing sewer gas or septic odors is a special edition of our more general advice on finding and curing sewage odor problems. Here we focus on sewage or septic odor problems that occur during cold weather or wet weather.

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.

The Short Answer to Diagnosing Bad Smells: Septic Odors in Cold Weather

1. Locate the outdoor septic components - septic tank and fields, or their probable location. Melted areas of snow can be helpful as they often mark the location of even properly-working septic system components - the soil is warmer at the septic tank and at the drainfield lines.
   
   As in the two photographs of snow over septic fields (left) and over a septic tank (right), if you see snowmelt, the system is probably not frozen. Warm effluent is entering from the septic tank and bacterial action is progressing in the soils. If you do not see septic effluent coming to the surface of the yard and if drains are not backing up inside the outdoor parts of the septic system appear to be working. But how do we know if the septic system is frozen and not accepting waste from the building? What if we think the septic system is blocked by freezing? See Septic Inspection Testing for details.
2. Before doing anything costly it's important to do your best to properly diagnose the problem. Do NOT hire a company to "rejuvenate" your septic field nor to install or flush or use any other magic product. It would be a better investment to take the cash you'd have paid them and rip it into small pieces and flush it down the drain.
3. Frozen septic fields: A septic system can become frozen in prolonged very cold weather if the system is also not in regular use. If the septic field froze and stopped accepting effluent, or if it were totally blocked and in failure (see below), your entire septic system would back up as you used the building drains, and you'd see drains backing up into the lowest areas of the home like a basement toilet or sink. I don't mean odors, I mean sewage backup.
4. Partial septic blockage: If a building drain or septic system or system drainfield is partially blocked, it's possible for that condition to generate odors in or out of the building. In this case odors often 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.

   If you're using the system and it's not backing up it's not so likely that the problem is a frozen septic field.

   There could be a drain vent line problem such as a frozen vent line (frost from moisture moving up the vent line above the roof from use of that drain for laundry or showering).

   Be sure the traps in the lower bath are not dry as a dry trap will often send sewer gases into a building..

   Check out the above items first.

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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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