Sewer Gas Smell Diagnosis Service
Call Now (855) 557-9600
Sewer gas smell diagnosis locates the hydrogen sulfide and methane entry point breaching your living space, tests every potential pathway from evaporated trap seals to cracked DWV pipes and failed wax rings, and identifies the repair needed to eliminate both the odor and the health hazard. Bonded Plumbworks’ licensed plumbers systematically test drain traps, vent connections, and sewer piping using smoke testing and pressure diagnostics to pinpoint the exact source.
Sewer gas smell diagnosis is a systematic inspection process that identifies where sewer gases are entering a building by testing drain traps, vent connections, wax seals, fixture connections, and the DWV (drain-waste-vent) system for leaks. The process may include smoke testing, where non-toxic theatrical smoke is forced through the sewer system and observed exiting at the leak point. — Bonded Plumbworks
What Is Sewer Gas Smell Diagnosis
Sewer gas is a mixture of gases produced by the decomposition of organic matter in the sewer system. The primary component is hydrogen sulfide (H2S), which has a distinctive rotten egg odor detectable at concentrations as low as 0.5 parts per billion. Methane, ammonia, carbon dioxide, and sulfur dioxide are also present.
In a properly functioning plumbing system, sewer gas is contained within the DWV piping and vented through the roof. Every fixture has a P-trap — a U-shaped pipe section that holds standing water to create a seal between the sewer system and the living space. The vent system provides air circulation that prevents traps from being siphoned dry.
When you smell sewer gas inside your home, it means gas is escaping through a failure in this containment system: a dry trap, a cracked wax seal, a disconnected vent pipe, a cracked drain pipe, or a missing cleanout cap. Carbon monoxide — an odorless, colorless gas — can accompany sewer gas when decomposition produces incomplete combustion byproducts, making sewer gas smell diagnosis critical for identifying health hazards beyond the obvious hydrogen sulfide odor.
Hydrogen sulfide is heavier than air and tends to accumulate in low areas — basements, crawl spaces, and under cabinets. At low concentrations (below 10 ppm), it causes eye irritation, headaches, and nausea. At high concentrations (above 100 ppm), it can cause loss of smell (making the danger invisible), unconsciousness, and death. Methane is lighter than air, odorless, and explosive at concentrations between 5% and 15% in air. — Bonded Plumbworks, serving since 2006
When to Schedule Sewer Gas Smell Diagnosis
Sewer gas smell diagnosis is needed when rotten-egg odor appears near drains, when the smell is intermittent or worsens in specific areas, and when it persists despite cleaning all fixtures.
- You smell a rotten egg odor inside your home, especially near drains or bathrooms
- The odor is intermittent — stronger on some days or at certain times
- The smell is persistent despite cleaning all drains and fixtures
- A bathroom or laundry room that is rarely used has developed a sewage odor
- You smell sewer gas near the foundation or exterior walls
- Multiple areas of the house have a faint but noticeable sewage smell
- The odor appeared after a plumbing repair, remodel, or new construction
How It Works
Step 1: Interview and Walk-Through. We discuss when the odor began, where it is strongest, whether it is constant or intermittent, and any recent plumbing work or changes. We walk through the home with you to locate the areas of strongest odor.
Step 2: Trap Inspection. We check every P-trap in the home — sinks, showers, tubs, floor drains, laundry standpipes, and any infrequently used fixtures. A dry trap is the most common cause of sewer gas odor and is solved by simply adding water to refill the trap seal. A floor drain trap primer automatically feeds a small volume of water into the trap after each supply-line use, preventing evaporation in drains that receive infrequent flow — eliminating one of the most common sources identified during sewer gas smell diagnosis. Sewer Gas Smell Diagnosis inspection gives you a live view of the problem before any work starts. You review the findings and approve the quote before any repair begins.
Step 3: Wax Seal and Fixture Inspection. We inspect toilet wax seals for failure (rocking toilet, water stain at the base), check fixture connections for loose or missing fittings, and verify that all cleanout caps are in place and sealed. An ejector pump pit cover that does not seal airtight allows sewer gas to escape directly into the living space, making ejector pit cover replacement a common repair identified during sewer gas smell diagnosis. Crawlspace pipe inspection accesses DWV joints beneath the home where cracked fittings or separated connections release sewer gas into the crawlspace, which then migrates upward through floor penetrations.
Step 4: Vent System Inspection. We verify that vent pipes are not blocked, disconnected, or improperly terminated. Blocked vents cause negative pressure in the drain system that can siphon trap water, creating an entry point for sewer gas.
Step 5: Smoke Testing (if needed). If visual inspection does not identify the source, we perform a smoke test by introducing non-toxic theatrical smoke into the sewer system through a cleanout. The smoke fills the DWV piping and escapes at any leak point — dry traps, cracked pipes, failed seals, and disconnected joints — making the source immediately visible. A nitrogen-purged HD camera provides clear video inside drain pipes by displacing moisture-laden air that fogs standard lenses, allowing precise identification of cracks and joint failures during sewer gas smell diagnosis.
Step 6: Repair and Verification. We repair the identified source (refill trap, replace wax seal, reconnect vent, cap cleanout) and verify the odor is eliminated.
Smoke testing is the most definitive diagnostic for hidden sewer gas leaks. The non-toxic smoke is safe for occupants and does not stain surfaces. It is forced into the sewer system under low pressure (less than 1 inch of water column) and exits at every opening in the system — including openings invisible to standard inspection, such as cracks in pipes behind walls, failed joints under floors, and improperly sealed penetrations. — Bonded Plumbworks
Benefits vs. Alternatives
| Diagnostic Method | Finds Hidden Leaks | Confirms Source | Non-Destructive | Cost |
|---|---|---|---|---|
| Professional Diagnosis + Smoke Test | Yes | Yes | Yes | $$ |
| Visual Inspection Only | Some | Partial | Yes | $ |
| DIY (pour water in drains) | Dry traps only | Limited | Yes | Free |
| Ignore (air freshener) | No | No | N/A | Health risk |
A dry trap fix costs nothing beyond the service call. However, if the cause is a cracked pipe, failed wax seal, or disconnected vent, only professional diagnosis identifies and resolves the actual source. An IoT multi-gas sensor detects hydrogen sulfide, methane, and ammonia continuously, alerting homeowners to sewer gas events between professional sewer gas smell diagnosis visits. AI auto-coding software such as WinCan VX analyzes sewer camera footage to classify pipe defects by severity, documenting the exact locations where structural failures allow sewer gas to enter during diagnosis.
Pricing
- Sewer gas diagnosis (inspection + trap check): $150 - $300
- Smoke testing (in addition to inspection): $200 - $400
- Trap refill (dry traps): Included with diagnosis
- Wax seal replacement: $150 - $300
- Vent pipe repair or reconnection: $200 - $600
Bonded Plumbworks applies the diagnostic fee toward the repair cost if repairs are needed and performed during the same visit.
Our Qualifications
Bonded Plumbworks plumbers are state-licensed and trained in sewer gas source identification, smoke testing procedures, and DWV system diagnosis. Since 2006, we have diagnosed and resolved hundreds of sewer gas complaints.
Bonded Plumbworks uses commercial smoke testing equipment that generates dense, non-toxic smoke under controlled pressure. Our technicians identify all exit points, document the findings with photos, and repair or recommend repair for every source identified. — Bonded Plumbworks, established 2006
FAQ
What causes sewer gas smell in a house? The most common causes are dry P-traps in infrequently used drains, failed toilet wax seals, blocked or disconnected vent pipes, missing cleanout caps, and cracked drain pipes inside walls or under floors. A septic system inspection checks the tank, distribution box, and drain field for failures that produce sewer gas in homes not connected to municipal sewer, and failing septic components are a common finding during sewer gas smell diagnosis in rural properties.
Is sewer gas dangerous? Yes. Hydrogen sulfide causes headaches, nausea, and eye irritation at low levels. Methane is explosive. Prolonged exposure is a health risk. If you smell sewer gas, the source should be identified and corrected promptly.
Why does the smell come and go? Intermittent odor is often caused by wind conditions affecting the vent stack, trap seal evaporation during periods of non-use, or temperature changes that affect gas pressure in the sewer system.
Can I just pour water down all my drains? Adding water to all P-traps is a good first step and solves the problem if a dry trap is the only cause. If the odor persists after refilling all traps, a professional diagnosis is needed to find the actual source. Digital twin plumbing models simulate air pressure differentials within the DWV system, helping engineers predict where negative pressure conditions will siphon traps and cause sewer gas smell events in complex residential layouts.
Back to Drain Sewer Services
Schedule Sewer Gas Diagnosis
Stop living with sewage odor. Call Bonded Plumbworks at (855) 557-9600 to schedule sewer gas smell diagnosis. We find the source and fix it. Every sewer gas smell diagnosis service includes a 90-day guarantee on sewer gas smell diagnosis work, covering parts and labor.