Sewer Gas Smell in a Home: Causes and Next Steps

Common causes of sewer-like odors

• A rarely used floor drain, shower or sink may have a dry trap that no longer blocks odors from the drain system.
• Residue in a sink overflow, drain opening or trap can create an unpleasant smell near one fixture.
• A loose, damaged or poorly sealed drain connection may allow odors to escape indoors.
• A blocked or damaged plumbing vent can interfere with normal drainage and allow odors to return.
• Recurring clogs or backups may point to a larger drain or sewer-line issue that needs diagnosis.

What to check safely

• Notice which room or fixture has the odor and whether it changes when nearby plumbing is used.
• If a rarely used fixture is involved, run water briefly to refill its trap. Stop if water backs up or leaks appear.
• Do not mix drain chemicals or keep adding cleaner to a slow or blocked drain.
• If the odor persists, returns quickly or occurs with bubbling drains or backups, arrange a plumbing assessment.

When a sewer camera inspection may help

A camera inspection may help when recurring backups, suspected roots or a damaged section are part of the symptoms. A camera only shows accessible portions of a line; standing water, heavy buildup or a complete blockage can limit visibility.

Read when a sewer camera inspection makes sense or learn about sewer camera inspections in San Diego County.

Common questions

Can a dry drain trap cause a sewer smell?

Yes. A trap holds water that helps block odors from the drain system. A rarely used fixture may need water added to restore that barrier.

Does a sewer smell always mean the main line is blocked?

No. Odors can have several causes, including a dry trap, residue, a vent issue or a drain connection problem. A plumber can assess the location and symptoms.

Should I use chemical drain cleaner?

Avoid mixing products or repeatedly pouring chemicals into a slow or blocked drain. The wrong product can create a hazard or complicate the next repair step.