Table of Sewer or Septic Odor & Gas Odor Sources©
List of where smells may originate inside or outside of buildings

Table of Sources of Sewer or Septic Gases & Odors In & Around Buildings©

This table lists sources of sewer, septic, sulphur, or hydrogen sulfide odors in buildings, organized alphabetically by source.

To track down an unidentified odor or smell by the smell characteristic see ODOR DIAGNOSIS SIX STEPS.

See TRACK SEPTIC / SEWER ODOR to SOURCE for homes connected to private septic systems

or see TRACK SEWER ODOR to SOURCE for homes connected to public sewer systems.

Sewer or Septic Odor Source

Location of Odor

Diagnosis & Repair Articles

Air conditioning and heating systems 

using air ducts and blower fans can pick up odors from one source and move them to another destination.

In some cases local negative air pressure may also overcome normal drain pipe venting, especially if plumbing traps are omitted or defective or if there are loose toilets leaking odors into a room.

Septic Odor from Air Conditioner.

DUCT SYSTEM DESIGN SIZE & DEFECTS

ODORS in DUCT WORK

Air conditioning / heat pump condensate drain connections:

an improper connection of the condensate drain from an A/C or heat pump system directly to a sewer line or drain / waste / vent piping system

can permit back-drafting of sewer gases through the drain system and into the HVAC system air handler where in turn it may pass through the HVAC ducts into other building areas.

Crawl space odors of septic, sewer, or dead animals.

Check for drain leaks, fuel piping leaks, dead animals, chemical or pesticide applications, debris, mold, soil gases.

Drain trap odors:

Found sewer gas odors at plumbing fixture traps whose water trap was lost due to trap siphonage due in turn to missing, improperly installed (too distant), or blocked plumbing vent piping.

Where dry plumbing traps pass sewer gases back into a building the problem may be worse in cold weather or when building vent fans are decreasing the in-building air pressure, drawing gases out of drain piping

BACKDRAFTING HEATING EQUIPMENT

BUILDING DRAIN ODOR SOURCES

DRAIN PIPING & SEWER ODORS

LEAKY TOILET SEALS, ODORS

SEWER GAS ODORS in COLD / WET WEATHER

GAS LEAK DETECTION, LP / NG

Gas Piping and Tank Defects

METHANE & SEWER GAS HAZARDS

METHANE GAS SOURCES

Electrical conduit leaks:

found septic gases following electrical conduit from septic pumping station into the principal building

MOLD ODORS, MUSTY SMELLS

MVOCs & MOLDY MUSTY
ODORS

Plumbing vent odors,

observed indoors (leaky plumbing vents, missing plumbing vents, vents not extended outside) or observed outdoors (downdrafts, bad location)

Septic system drainfield failure, no visible effluent

Private Septic System Failures:

Found sewer gas leaks outside due to a failing septic drainfield and/or blocked sewer piping causing backups that leaked outdoors.

In a case where odors were traced to leaks at a septic tank, 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.

DRAINFIELD ODORS, FAILURES

BACKDRAFTING & SEWER/SEPTIC ODORS

DRAINFIELD ODORS, FAILURES

LAGOON SEPTIC SYSTEMS

PLUMBING VENT PIPING

SEPTIC TANK LEAKS

SEPTIC TANK INSPECTION PROCEDURE - home

SEPTIC TANK LEVELS of SEWAGE

SEWAGE PUMPS

SEWAGE PUMP DAMAGE & REPAIR

SEWAGE PUMPS

SEWAGE PUMP DAMAGE & REPAIR

SEWAGE BACKUP, WHAT TO DO

SEWAGE CONTAMINATION in BUILDINGS

Sewage grinder pump leaks & odors 

• Check valve failure, backup
• Check for a loose, damaged, or lost cover gasket at the sewage grinder pump
• Check for a clogged vent on the sewage grinder pump (not present on all systems)
• Pour clean water into the sewage grinder pump or ejector pump pit sufficient to pump out sewage water before leaving the system out of use for a month or longer.

SEWAGE EJECTOR / GRINDER PUMPS

SEWAGE PUMP ODORS

Sewer/Septic Piping Leaks:

Found DWV (drain-waste-vent piping) plumbing piping leaks: had a plumber pressure test the drain waste vent piping to find sewer gas leaks due to mechanical damage, rust, corrosion in piping, improper sewer vent locations, or inadequate/missing waste pipe venting. Also

• Sewer Piping Joint Leaks:
  
  Found sewer gas leaks where plastic pipes had never been properly glued in a wall, ceiling or floor, from original construction. Found by pressure testing.
• Sewer Piping Punctures:
  
  Found sewer gas leaks where drain waste vent pipes had been perforated by a nail from flooring or in one case from hanging a picture on the wall

DRAIN LINE PIPE LEAKS (drain line or sewer line breaks, leaks, seeps)

DRAIN ODOR SOURCES

DRAIN PIPING & SEWER ODORS

Sink odors:

smells coming from or beneath sinks. Slow drains, gurgling drains, blocked drains, leaks, can all be sources of smells around bath, kitchen, & laundry sinks

BACKDRAFTING HEATING EQUIPMENT

DRAIN LINE PIPE LEAKS

DRAIN PIPING & SEWER ODORS

DRAIN ODOR SOURCES

FIXTURE vs SYSTEM DRAIN BLOCKAGE

FLOOR DRAIN / TRAP ODORS

PLUMBING FIXTURE TRAPS

PLUMBING SYSTEM NOISE DIAGNOSIS & CURE

PLUMBING VENT DEFECTS & NOISES

Swamp gas or marsh gas:

Traced sewer/septic gas odors to swamp gases or marsh gas, also potentially dangerous, especially if swamp gas leaks into and accumulates inside a building, as reported in the NY Times, appears to have occurred in Cancun, Mexico in November 2010.

Swamp gases include methane produced by the decomposition of organic materials in subsoils.

Outdoors

FIXTURE vs SYSTEM DRAIN BLOCKAGE

PLUMBING VENT DEFECTS & NOISES

LEAKY TOILET SEALS, ODORS

TOILET REPAIR GUIDE

Water heater anode failure or water heater tank bacteria

Other sulphur type gas odors: traced to gases or chemicals in private water supply, well water contaminants, or traced to bacterial contamination of a water heater or corroded water heater anode

ANODES & DIP TUBES on WATER HEATERS

SULPHUR & SEWER GAS SMELL SOURCES

Water supply contaminants

ODORS IN WATER

SULPHUR & SEWER GAS SMELL SOURCES