Why this matters
Sewer gas is unpleasant and can indicate a problem in the drain system. Most odours have simple causes.
Common causes
| Source | Cause |
|---|---|
| Floor drain | Dry trap |
| Bathroom basin | Dirty overflow channel |
| Kitchen sink | Grease and food in the trap |
| Toilet base | Failed wax seal |
| Whole house | Vent blockage or cracked pipe |
A slow drain is a partial clog telling you where it lives. Ignore it and it becomes a full one at the worst hour.
Step by step
- Pour water into rarely used drains to refill traps.
- Clean basin overflows with a bottle brush.
- Remove and clean the kitchen trap.
- Check the toilet for rocking or stains at the base.
- Notice whether the smell is worse in certain weather, which can point to venting.
Odours that point to something bigger
A smell that comes and goes with the wind, or that appears in several rooms at once, can mean a cracked vent pipe in a wall or attic, a loose cleanout plug in the basement, or a dried trap in a rarely used fixture you have forgotten about, such as a basement shower. In older Markham houses with cast iron stacks, a hairline crack can leak sewer gas without ever leaking water. A smoke test, where harmless smoke is pushed into the drain system, shows exactly where gas escapes. If you smell rotten eggs near a gas appliance rather than a drain, treat it as a possible gas leak and leave the house.
Handing it over to us
Call if the smell persists, appears throughout the house, or comes from walls. See floor drain repair, drain cleaning and toilet repair.
Markham note: village-core houses tend to hide cast iron and galvanized behind plaster, while Cornell and Box Grove builds run PEX to a manifold. We ask the year your house was built so the right fittings ride along on the truck.
Straight from the phone log
Can a vent problem cause smells?
Yes. A blocked vent can siphon traps dry.
Why does my bathroom smell after a shower?
Steam can release odours from a dirty drain; cleaning it usually helps.
Ready to get it fixed?
One call, a clear explanation, and work finished tidily before we leave.