Tracking down a sewer smell

Start with the easy ones

1. Dry floor drain. Pour a bucket of water in. If the smell fades in an hour, that was it.
2. Unused shower or sink. Guest bathrooms dry out. Run each tap for a minute.
3. Laundry tub without a trap. Common in older basements.

Smell near a toilet

When the wax seal fails, gas leaks out around the base without always leaking water. Rock the toilet gently; if it moves, the seal is likely broken. Brown staining on the floor or the ceiling below confirms it.

When the wax seal fails, gas leaks out around the base without always leaking water.

From the counter

Smell when draining

If gurgling and a whiff come together when a fixture drains, the vent may be blocked by a bird nest, leaves or ice, or the fixture may not be vented at all. Water drains and pulls the trap dry behind it. Basement bathrooms added without proper venting are frequent offenders.

Smell that will not go away

• Cracked cast iron stack behind a wall
• Loose cleanout cap on the main drain
• Broken drain under the basement slab
• Sewage ejector pit lid not sealed

A plumber can do a smoke test, pushing harmless smoke into the drain system and watching where it comes out. That finds cracks and loose joints quickly.

North York homes

Cast iron stacks in 1950s houses can crack along their length, leaving a dark rust line. Cleanout caps in old front-wall basements get loosened by past clearing jobs and never tightened properly. Both are common, both are quick to fix once found.

Questions

Next on the shelf

• Toilet repair
• Basement floor drain backups
• Sewer camera inspection