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ODORS GASES SMELLS, DIAGNOSIS & CURE
PLUMBING SYSTEM INSPECT DIAGNOSE REPAIR
ANODES & DIP TUBES on WATER HEATERS
BACKUP PREVENTION, SEPTIC
BACKUP PREVENTION, SEWER LINE
BACKWATER VALVES, SEWER LINE
CHEMICAL CONTAMINANTS in WATER
CHLORINE IN DRINKING WATER
DEPTH of SEPTIC TANK
DRAIN & SEWER PIPING
FLOOD DAMAGE ASSESSMENT, SAFETY & CLEANUP
FLOOR DRAIN / TRAP ODORS
GAS PIPING, VALVES, CONTROLS
HARD WATER - SOFTENERS
METHANE GAS SOURCES
ODORS GASES SMELLS, DIAGNOSIS & CURE
ODORS IN WATER
ODORS, SEPTIC or SEWER
ODORS SEWER GAS in COLD WEATHER
ODORS, SULPHUR SMELL SOURCES
ANIMAL or URINE ODOR SOURCE DETECTION
PIPING IN BUILDINGS, Clogs Leaks Types
PLUMBING FIXTURES, KITCHEN, BATH
PLUMBING NOISE CONTROL
PLUMBING VENT DEFINITIONS & CODES
PLUMBING VENT DEFECTS & NOISES
REPAIR BURST LEAKY PIPES
SEPTIC METHANE GAS
SEPTIC SYSTEM INSPECT DIAGNOSE REPAIR
SULPHUR & SEWER GAS SMELL SOURCES
TOILETS, INSPECT, INSTALL, REPAIR
WATER TESTS, CONTAMINANTS, TREATMENT
WINTERIZE A BUILDING
Cold weather sewer or septic odor troubleshooting: this article series 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.
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Smelling sewage odors inside only, or mostly inside
Here are some places to look and perhaps to fix if you're smelling sewage or septic like odors inside of a building:
You can usually spot inadequate or blocked plumbing venting by noticing, for example, that tub, shower, or sink drain makes a gurgling or "glub glub" sound when a nearby toilet is flushed or when a full fixture is being drained. Inadequate or blocked plumbing venting can also mean that a plumbing fixture does not drain well (even though the drain line is not blocked). Inadequate venting produces a glub glub sound as water passes down a drain and cannot draw air in after itself through a plumbing vent stack.
Instead the drain has to draw air in to itself through various plumbing traps which, as they normally contain water, produces the glub glub sound as air passes through the trap. This defect can siphon water out of traps and let sewer gases back into a home - smelly and potentially dangerous (methane gas).
Also see Drain Noises: may indicate defective or clogged plumbing: how to diagnose and cure drain sounds
Cold Weather and Plumbing Vent Blockage Problems as a Source of Building Smells, Septic or Sewage Odors
What's different in cold weather that could cause indoor sewer gas odors only during freezing weather?
If in cold weather a plumbing vent pipe is frosting up, sewer gases may vent backwards out through building drains. In that case, even re-priming building drain traps won't prevent sewer gas entry as flushing a toilet or running a nearby drain can siphon water out of a nearby trap.
A thoughtful reader, Jill Elwert, suggested insulating the vent piping to try to delay vent pipe blockage by freezing moisture. We are afraid that even if you insulate the vent line in a cold attic, it'll freeze above the roof surface outdoors. You could try it but if that proves the problem, ultimately you'll want to have a plumber or handyman install a 2" or larger diameter vent from the attic floor up through the roof. See Remedies for Sewer Odors.
Diagnosing frozen plumbing vent lines:
See Plumbing Vent Defects for diagnostic details.
Freezing weather can cause a complete blockage of a plumbing vent stack by frost. For example steam from long showers moves up the vent pipe where it freezes in the pipe section extending above the building roof.
The absence of venting (missing or blocked) causes plumbing trap siphonage and loss of water in building traps. (Water flowing down a drain line without a nearby supply of makeup air to follow the water creates a vacuum that pulls water out of nearby plumbing traps. Flushing a toilet can siphon out a nearby sink or tub trap.)
What happens when the water seal is lost from a plumbing trap?
When the water seal is lost from a plumbing trap sewer gases can back up out of that fixture and not just smell bad. Sewer gases contain methane which is an explosive gas - possibly quite dangerous. In addition to occasional methane gas explosions inside buildings, I've had a report of an outdoor septic tank explosion too when an owner built a brush fire atop the tank.
In sum, dry plumbing traps are caused by evaporation at an unused fixture, leaks at the trap, or siphonage due to improper plumbing vent line installation. Dry traps can leak smelly or dangerous sewer gases into a building.
Check for dry plumbing traps, particularly at un-used basement or lower floor fixtures and at floor drains which might be connected to the sewer line. "Dry trap" means that there is no water in the trap bend or weir.
See Plumbing Vent Defects for diagnostic details of venting problems and see PLUMBING FIXTURE TRAPS for fixture trap inspection and defect diagnosis. Also see METHANE GAS SOURCES and see our broad-scope article on diagnosis and cure of sewer gas and septic odors: SEWER GAS ODORSdiagnosing, finding, and curing septic tank and sewer line smells. For more general guides see ODORS & SMELLS DIAGNOSIS & CURE for procedures to diagnose and cure all kinds of odors in and around buildings.
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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.
Design Manuals for Septic Systems
Onsite Wastewater Disposal Books