What Causes Smelly Drains?

Smelly drains are usually caused by trapped food, soap scum, or organic buildup in pipes, a dry or faulty water trap, or bacteria in the drain line. To fix the smell, flush the drain with boiling water and vinegar, clean the trap if accessible, and ensure water seals are intact. If the smell persists, a licensed plumber may need to inspect for a deeper blockage or sewer gas leak.

What Causes Smelly Drains in Wollongong Homes?

1. Organic Buildup in the Drainpipe
Food scraps, soap, grease, and hair collect in the drain over time. This organic matter decays and breeds bacteria, leading to sulphur-like or musty smells.

2. Dry or Faulty Water Trap (P-Trap or S-Trap)
Your drain trap is a curved section of pipe that holds water to block sewer gases. If it dries out due to infrequent use or incorrect installation, gas can escape into your home.

3. Blocked Vent Pipes
Plumbing vents regulate pressure and direct sewer gas safely out of your roof. If blocked by debris, birds’ nests, or corrosion, gases may be forced back down into your drains.

4. Cracked or Damaged Pipes
Old pipework—especially in older Wollongong suburbs—can leak gas or allow debris to settle in sections, creating stagnant pockets.

5. Incorrect Appliance Installation
DIY installations, especially of washing machines or dishwashers, may lack proper traps or have open ends, allowing odours to escape.

Quick Fixes You Can Try Yourself

Flush the Drain
Pour boiling water followed by a mix of vinegar and bicarbonate soda down the smelly drain. Let it fizz for 10–15 minutes, then flush again with hot water. This helps break up organic buildup.

Check the Trap
Remove and clean the U-bend trap under sinks if accessible. Wear gloves and prepare for smells it may be blocked with hair, sludge, or grease.

Top Up the Water Trap
If a drain hasn’t been used for a while (guest bathroom, floor waste), pour a few cups of water into it to restore the water seal.

Ventilate the Area
Use fans or open windows to disperse any gases until the issue is resolved. Avoid using chemical cleaners which may worsen pipe corrosion.

When to Call a Licensed Plumber

If smells persist despite cleaning, or if multiple drains across the house are affected, it’s time to bring in a professional. Persistent odours may indicate:

• A blocked main drain line
• A breach in sewer pipework
• A faulty or collapsed P-trap
• A ventilation issue inside walls or ceiling cavities

A licensed plumber will use inspection cameras or smoke testing to locate the cause. For homes affected by salt air or ageing pipework, we also recommend a system-wide drain inspection or pipe relining service.

If your case is urgent such as sewage smells in living areas our emergency plumbing service is available 24/7 across the Illawarra.

Preventing Drain Smells in the Future

• Avoid pouring grease or oils down the kitchen sink
• Clean drain strainers weekly
• Run boiling water down bathroom and laundry drains monthly
• Flush lesser-used drains seasonally to maintain trap water seals
• Schedule an annual plumbing checkup with a licensed local provider

Final Advice for Wollongong Homeowners

Drain smells are more than just unpleasant. They signal trapped waste, missing seals, or worse leaks and ventilation problems that could grow into major health or structural issues.

In Wollongong’s mix of new estates and older homes, smells often come from simple build-up but sometimes point to deeper faults hidden behind walls or under concrete.

Don’t just mask the smell. Find the cause. Fix it at the source. And if DIY doesn’t cut it, trust a licensed plumber like us at CS Plumbing Services who knows how your home was built and how to keep it safe.