Why Does My Drain Smell So Bad?
Smelly drains are one of the most common (and annoying) plumbing complaints in Australian homes. That rotten egg, musty, or sewer-like smell coming from your sink or shower is often a sign of something more serious than just bad luck.
If you’ve tried home remedies but the bad smell keeps coming back, it’s time to figure out what’s really going on — and whether you need to call a professional plumber.
Top 5 Causes of Smelly Drains
1. Dry P-Traps
Your P-trap is the U-shaped pipe under your sink or floor drain. It holds water to block sewer gases. If a sink or drain isn’t used often, the water evaporates — letting smells rise up into your home.
2. Bacterial Buildup
Hair, soap, toothpaste, food scraps, and other organic matter can get stuck inside your drain pipes. Over time, bacteria break it down — creating sulphuric, eggy odours.
3. Blocked Drain Vent
Every plumbing system is vented to release gas. If your vent pipe is blocked (e.g., by leaves, nests, or rust), those gases have nowhere to go — so they back up into your bathroom or kitchen.
4. Mould or Mildew in Pipes
Some bathroom drains, especially in older homes, develop internal mould colonies due to damp conditions. This causes a musty or earthy smell even when the drains are clear.
5. Sewer Line Issues
If multiple drains smell or you hear gurgling after flushing the toilet, the problem might be a cracked or blocked sewer line — a more serious issue that needs immediate attention.
DIY Fixes for Smelly Drains
Before calling in a plumber, try these proven home remedies:
- Run hot water down the drain for 1–2 minutes to flush debris (don’t use boiling water on PVC pipes).
- Use baking soda and vinegar: Pour ½ cup baking soda and 1 cup vinegar down the drain, wait 15 minutes, and flush with hot water.
- Manually clean the P-trap: If you’re confident, disconnect and rinse the P-trap under the sink.
- Use a drain brush or zip tool to remove hair and debris from bathroom drains.
- Pour water into unused drains once a month to keep traps sealed.
When to Call a Plumber for Smelly Drains
DIY tricks are fine — but if the smell keeps returning or you notice other warning signs, it’s time to get professional help. Here’s when to book a plumber:
✅ Persistent Bad Smell
If you’ve cleaned the drain and the smell returns within days, the problem may be further down the line — or outside your home entirely.
✅ Multiple Drains Affected
Smells coming from more than one sink or shower? It’s probably a blocked vent or a damaged sewer line.
✅ Gurgling Sounds
If your drains gurgle or bubble after flushing or draining, it may be air trapped by a blockage — a clear red flag.
✅ Water Backing Up
If water comes back up from other drains (e.g., you flush the toilet and the shower drain bubbles), call a plumber ASAP.
How Plumbers Fix Smelly Drains
At RJT Plumbing and Gas, we use professional tools to identify and fix the root cause — not just mask the smell.
🔍 CCTV Drain Camera Inspection
We look inside your pipes with high-definition cameras to find buildup, clogs, or cracks.
💦 High-Pressure Water Jetting
Our hydro jet equipment blasts away grease, sludge, and debris that cause smells and slow drainage.
🛠 Vent and Sewer Line Repairs
If the issue is structural or related to air pressure, we’ll diagnose and repair it to stop smells at the source.
📋 Drain Maintenance Plans
We offer regular servicing for households prone to blockages (especially in older homes or homes with tree roots nearby).
Common Questions About Smelly Drains
Q: Why does my bathroom drain smell like sewage?
A: It’s usually due to a dry P-trap or a blocked vent allowing sewer gases into your bathroom.
Q: Can I use bleach to fix a smelly drain?
A: Bleach can help with bacteria short-term, but it can damage pipes over time and doesn’t solve deeper issues like blockages or vent problems.
Q: My kitchen sink smells but isn’t blocked — why?
A: Grease and food particles may be coating your pipes. Bacteria feed on this residue, causing smells even when water flows normally.
Q: Is this something I can ignore?
A: Not if it’s persistent. Smelly drains often indicate a growing problem that can lead to backups or costly repairs later.
Take Action: Book a Drain Inspection Today
Don’t wait until a bad smell turns into a major plumbing issue. RJT Plumbing and Gas is your trusted partner for:
- Smelly drain diagnosis
- Sewer line repairs
- Drain maintenance plans
📞 Contact us to get your drains sorted — fast, safe, and clean.
