If your sink smells unpleasant even after cleaning, the cause is usually buildup inside the trap, blocked venting, or stagnant water rather than a broken pipe.
Most sink odours come from trapped debris or sewer gases escaping.
The Most Common Reasons This Happens
1. Dirty U-Bend (Trap)
The curved pipe beneath the sink holds water to block sewer gases.
If debris collects inside, it can rot and produce odours.
This is one of the most common causes.
If your sink also drains slowly, see:
→ Why Is My Sink Not Draining?
2. Food or Grease Buildup
In kitchen sinks, grease and food particles can coat the inside of pipes and begin to smell over time.
3. Dry Trap (Unused Sink)
If a sink hasn’t been used for a long time, the water inside the trap can evaporate.
Without this water seal, sewer gases can rise.
4. Blocked Vent Pipe
If the plumbing vent is blocked, sewer gases may escape through the sink.
If you also hear bubbling or gurgling, see:
If toilets are affected too:
5. Deeper Drain Line Issue
If odours are strong and persistent, the issue may be further down the drain line.
See:
Is This Serious?
It may be minor if:
- The smell improves after cleaning
- Only one sink is affected
- The trap hasn’t been cleaned recently
It may require attention if:
- Multiple drains smell
- You notice bubbling
- Water backs up
Persistent sewer smells should not be ignored.
What You Can Do
If your sink smells, you can:
- Clean the trap
- Flush with hot water
- Run water in unused sinks
- Monitor other drains
If the smell persists or spreads, inspection may be required.
For related issues, see:
→ Sink & Drain Problems Explained
→ Why Is My Sink Not Draining?
→ Why Is My Sink Gurgling?
→ Why Is My Toilet Gurgling?
→ Plumbing Problems Explained