How to Fix a Smelly Drain

A stinky drain is usually a dry P-trap, biofilm buildup, or a venting issue — not the mystery it seems.

Common causes

• Dry P-trap letting sewer gas up
• Biofilm buildup in the overflow
• Failed or blocked vent stack
• Broken wax ring under a toilet

Step-by-step

1. 01Pour a litre of water down any drain you rarely use
2. 02Scrub the drain rim and overflow with a bottle brush and enzyme cleaner
3. 03Check that vent stacks on the roof are unblocked
4. 04Snug the toilet down and replace the wax ring if it rocks

When to call Northbridge

• Smell returns within a day of cleaning
• You smell sewage but every trap is wet
• Vent stack is blocked or damaged
• Toilet base is leaking or rocking