A foul smell coming from your drains is more than unpleasant — it can signal a real plumbing problem that needs attention. Here’s what causes smelly drains and what you can do about it.

Common Causes of Smelly Drains

1. Dry P-Trap

Every drain in your home has a P-trap — the U-shaped bend in the pipe beneath the plughole. This trap holds a small amount of water that acts as a seal, blocking sewer gases from rising into your home.

If a drain isn’t used regularly (a spare bathroom, laundry tub, or floor waste), the water in the P-trap evaporates and sewer gas escapes.

Fix: Run water through unused drains for 30 seconds every couple of weeks to keep the P-trap filled.

2. Blocked or Partially Blocked Drain

Food scraps, grease, hair, and soap scum accumulate in drains over time. As this buildup decomposes, it produces a nasty smell — even before the drain becomes fully blocked.

Fix: Try flushing with boiling water or a baking soda and vinegar mixture. If the smell persists, the blockage may be deeper and need professional clearing.

3. Damaged or Cracked Pipes

Cracked or broken sewer pipes allow sewer gas to escape into the ground around your home and seep through walls or floors. This is more common in older Melbourne homes with ageing clay or cast iron pipes.

Fix: This requires a professional inspection. A plumber can use a CCTV camera to locate the damage and recommend repairs.

4. Blocked Vent Pipe

Your plumbing system has vent pipes (usually on the roof) that allow air to flow and sewer gases to escape safely outside. If a vent pipe becomes blocked by leaves, birds’ nests, or debris, those gases are forced back through your drains.

Fix: Vent pipe blockages need a plumber to safely access and clear the obstruction.

5. Faulty or Missing Drain Seal

Floor waste drains (the round grates in your bathroom or laundry floor) have seals or traps that can deteriorate over time. A broken seal lets sewer gas through.

Fix: A plumber can replace the seal or install a new floor waste with a proper trap.

6. Sewer Line Issues

If the smell is widespread throughout your home and affects multiple drains, there could be a problem with the main sewer line — such as a break, blockage, or tree root intrusion.

Fix: This needs professional diagnosis and repair. A CCTV drain inspection will identify the issue.

Quick DIY Fixes to Try

Before calling a plumber, try these for mild odours:

1. Flush with boiling water — Pour a kettle of boiling water down the drain slowly
2. Baking soda and vinegar — Half a cup of each, let it fizz for 30 minutes, then flush with hot water
3. Clean the drain cover — Remove and scrub the plughole, strainer, or grate
4. Run unused drains — Fill dry P-traps by running water for 30 seconds
5. Check the overflow — Basin overflows collect grime; clean them with a bottle brush

When to Call a Plumber

Contact a professional if:

• The smell persists after trying DIY fixes
• Multiple drains in your home smell
• You notice gurgling sounds from drains
• There are slow drains accompanying the smell
• You suspect damaged or cracked pipes
• The smell is strongest near floor waste drains

How We Fix Smelly Drains

At Hankook Plumbing, we use professional methods to identify and fix drain odour problems:

• CCTV drain inspection — Pinpoints blockages, cracks, and damage
• High-pressure water jetting — Clears buildup and restores clean pipes
• Pipe repairs and relining — Fixes cracked or broken pipes without excavation
• Vent pipe clearing — Removes blockages from roof vents
• Trap and seal replacement — Restores proper gas barriers

Don’t live with smelly drains. Call Hankook Plumbing on 0407 756 172 to get the problem sorted.