Quick Answer:
If you notice a sewer-like smell after a recent city water outage while turning on taps, it’s most often caused by air, dislodged sediment, or dried traps in your plumbing rather than an immediate break in the municipal line. Start by flushing the service line and refilling traps inside the house; if the odor doesn’t go away, check neighbors and consider calling your water utility or a plumber. For a related situation, see Smell after turning water back on.
Why This Happens
- When water service is lost and then restored, pressure changes can pull air, sediment, or sewage odors into the service line or your home plumbing.
- Water in traps (the curved pipe under sinks, tubs, and floor drains) can be siphoned or evaporate during an outage, letting sewer gas into the house.
- Municipal main flushing or sudden pressure spikes can dislodge scale and gunk that appears and smells when first pushed into the home line.
- Low points—like basement floor drains or long service lines—can collect sediment that releases odor when disturbed.
Step-by-Step What to Do
Step 1 — Slowly open an exterior hose bib to flush the service line
Open a protected outdoor faucet slowly and let it run for several minutes. This flushes debris and any trapped water out of the service line. Direct the flow to a yard, driveway, or other suitable area—don’t route it into a sanitary drain.
Step 2 — Run cold taps and flush toilets sequentially to refill traps
Start at the lowest level of the house and work upward. Run each cold tap for a minute or two and flush each toilet once. Doing this sequentially helps refill traps and pushes fresh water through the system so sewer gas can’t enter through dry traps.
Step 3 — Check for trapped air and pressure swings by running multiple fixtures
If you see sputtering or experience pressure swings, run two or three fixtures at once (for example, a basement cold tap and an upstairs sink) to stabilize flow and help dislodge trapped air.
Step 4 — Inspect low points for dislodged sediment
Look at basement floor drains, sump discharge points, and any exposed low sections of pipe. If you see obvious sediment, clear loose debris with gloves and run the nearby faucets to flush it out. Avoid reaching into drains with bare hands.
Step 5 — If the smell persists, check neighbors to confirm a wider issue
Ask nearby homes if they smell the same thing. If multiple houses report the odor, the problem is likely municipal or in the shared main and should be reported to the water utility for investigation.
What Not to Do
- Don’t immediately assume it’s a private sewer problem—avoid backflushing or hooking garden hoses into drains; call a pro when odors continue after thoroughly flushing your house or neighbors report similar issues.
- Don’t pour strong chemicals down every drain in an attempt to “kill” the smell; that can damage plumbing and create hazardous fumes.
- Don’t block vents or cover floor drains while investigating; you want ventilation and normal trap function to return quickly.
When to Call a Professional
- If the odor remains after you’ve flushed the service line, refilled traps, and checked neighbors.
- If you see sewage backing up into drains or toilets, or if multiple fixtures show persistent problems.
- If neighbors confirm the smell over a wide area—contact your water utility first, then a licensed plumber if directed or if the utility reports no known mains work.
Safety Notes
- Sewer gas can contain hydrogen sulfide, which smells like rotten eggs and can be harmful in high concentrations. Vent the area by opening windows and doors.
- If anyone feels dizzy, nauseous, or short of breath, leave the house and seek fresh air; call emergency services if symptoms are severe.
- Wear gloves and eye protection when clearing debris from drains. Avoid entering confined spaces (crawlspaces, small basements) with strong odors alone.
Common Homeowner Questions
- Why did this start right after the outage? Pressure changes and flushing in the mains can move air and sediment into your service line and plumbing, producing temporary odors.
- How long should I expect the smell to last? Often it clears after thorough flushing and refilling traps—usually within a few hours to a day; persistent smells need further checks.
- Should I call the city or a plumber first? If neighbors also smell it, contact the water utility first; if it’s isolated to your home or there is backup, call a licensed plumber.
More in this topic
For more related fixes and similar symptoms, see Sewer Gas Smell from Floor Drains.