Typical signs
- Intermittent odour, gurgling, trap losing water or odour near a toilet.
Where it is often found
- Floor drains, rarely used bathrooms, basements, washers and vents.
What it can mean
- Dry trap, failed seal, blocked vent, cracked drain or network pressure.
What to check next
- Add water to rarely used traps.
- Identify the fixture and conditions that trigger the odour.
Reasonable immediate actions
- Ventilate the room and avoid flames if the source is unknown.
When to stop and call a professional
- Persistent odour, multiple fixtures, septic system, concealed drain or possible fuel gas.
Prevention
- Trap primers, maintained seals and proper venting/drainage.