Quick Answer:
If you open your house after a trip and notice a sewer smell, it’s usually because water in some plumbing traps evaporated while you were away or a rarely used drain drained itself. Start by running water through all fixtures to refill traps, add a pint of water to floor drains and seldom-used fixtures, and inspect for anything that could have broken a seal. If the odor continues after these checks, it may be a mechanical issue or backflow and you should call a professional.
Why This Happens
Most plumbing fixtures have a U-shaped trap that holds water to block sewer gases from coming into the house. When a home sits unused for days, that water can slowly evaporate and let odors through. Other causes include an open appliance drain or ice maker feature that auto-drains, a failed seal at a roof vent, or an unseen leak that lets sewer air into a wall or crawl space. In basements and low points, you might notice a stronger source—like a floor drain—that has dried out; see Sewer smell from basement drain for similar situations.
Step-by-Step What to Do
1. Walk through and run water in every fixture
- Turn on and run each sink for a few seconds, fill and drain tubs and showers, and flush every toilet. This refills the trap with fresh water.
- Open cabinet doors under sinks so you can check for leaks while you run fixtures.
2. Pour water into lesser-used drains and fixtures
- Pour about a pint (roughly a cup and a half) of water into floor drains, basement drains, laundry tubs, and other rarely used fixtures. This quickly restores the trap seal.
- If a drain has a removable trap cover, visually check the trap for debris before pouring water.
3. Inspect for leaks or signs animals disturbed seals
- Look for damp spots, new stains, or soft drywall near plumbing runs. A leak can carry sewer odors into living spaces.
- Check for rodent or pest activity around vents, crawl spaces, or foundation openings—animals can chew seals or dislodge caps.
4. Check appliance auto-drain features
- Some ice makers, water filters, and appliances have automatic drains or overflow features that open periodically. Confirm whether any appliance drained while you were gone.
- Reset or disable any auto-drain functions temporarily during your inspection if safe to do so, and ensure hoses are properly connected.
5. If the smell persists, check trap primers and mechanical devices
- Some homes use trap primers or mechanical devices that keep trap seals from evaporating. Verify these devices are functioning and that power or water supply to them wasn’t interrupted.
- If you have floor drain primer assemblies, inspect them for clogs or failure. If unsure, note the location and tell a plumber when you call.
What Not to Do
- Avoid using heavy fragrances or candles to mask the smell—this prevents proper diagnosis; call a pro when odors remain after refilling traps or if you find signs of backflow when you return.
- Do not ignore ongoing or strong sewer odors. Persistent sewer gas can point to a plumbing failure or backflow issue that needs attention.
When to Call a Professional
Call a licensed plumber if:
- You refill traps and the odor remains or returns quickly.
- You find signs of backflow, sewage stains, wet areas that suggest a leak, or if multiple drains are affected.
- You can’t locate possible failed mechanical devices like trap primers or are uncomfortable checking appliances that may have auto-drained.
A professional can pressure-test drains, inspect vents and seals, and trace hidden leaks or backflow sources safely.
Safety Notes
- Ventilate the house while you inspect—open windows and run fans to reduce odors.
- If you smell anything like natural gas or a very strong sewer gas, leave the area and call emergency services if you feel unwell. Do not use open flames indoors.
- Wear gloves when checking drains or cleaning up sewage-contaminated areas, and wash hands thoroughly afterward.
Common Homeowner Questions
- How long does a trap take to dry out? A: In warm, dry conditions a shallow trap can dry in a few days; deeper traps may take longer.
- Will bleach fix the smell? A: A quick bleach pour can help sanitize a surface but it won’t fix a dried-out trap or a mechanical failure; refill the trap with water first.
- Can a roof vent cause odors? A: Yes—if a vent cap is missing or blocked, sewer gases can behave unpredictably; a pro can inspect venting safely.
More in this topic
For more related fixes and similar symptoms, see Sewer Gas Smell from Floor Drains.