Drain Smells in Melbourne Homes — The Real Causes
A bad smell coming from a drain is one of the most common complaints we get from homeowners across Melbourne's South East. It's unpleasant, it can be a health concern, and it can be surprisingly hard to find the source. Here are the most common causes and what to do about each one.
1. Dry or Empty P-Trap
The P-trap is the curved section of pipe under sinks, basins and floor drains. It holds a small amount of water that creates a seal against sewer gases. If a drain isn't used regularly — a guest bathroom, a floor drain in a laundry — the water in the trap evaporates and sewer gas comes straight up through the drain. Fix: pour water down the drain to refill the trap. Add a small amount of cooking oil to slow future evaporation.
2. Blocked or Partially Blocked Drain
A build-up of hair, soap, grease or food debris in a drain creates a breeding ground for bacteria that produces that distinctive drain smell. If the smell is accompanied by slow drainage, you likely have a partial blockage. Professional clearing with a hydro jetter removes the organic material completely.
3. Cracked or Broken Pipe Leaking Sewer Gas
A cracked pipe in the wall, floor or underground doesn't just leak water — it leaks sewer gas. This is a more serious problem and requires a CCTV inspection or drain smoke test to locate. If you have a smell that appears and disappears, comes from multiple locations, or seems to come from inside a wall, this may be the cause.
Sewer gas contains hydrogen sulphide which has a rotten egg smell. In high concentrations it's a health hazard. If you have a persistent strong sewage smell inside your home, don't ignore it — have it professionally investigated.
4. Tree Root Intrusion
Tree roots in drain pipes allow sewer gas to escape through pipe joint gaps. The smell is typically outside or under the house, and is often accompanied by slow drainage. CCTV inspection will confirm root intrusion.
5. Blocked Vent Pipe
Plumbing vent pipes run through the roof to release sewer gases outside. If these become blocked — by debris, birds nests or leaves — gases are forced down through drain fixtures instead. A blocked vent is often identified by gurgling sounds from toilets and drains alongside the smell.
When to Call a Drain Smoke Test
If you've ruled out the simple causes above and the smell persists, a drain smoke test is the most reliable way to pinpoint the exact source. Call Jack at Water Serpent Plumbing on 0425 226 636.