If your bathroom sink smells bad but water drains normally, this is very common in UK homes.
The issue is usually bacteria in the waste pipe, a dry trap, or poor air venting — not a blockage.
Here’s the fastest way to fix it properly.
Direct Answer: Why Your Bathroom Sink Smells but Isn’t Blocked
The smell comes from biofilm buildup inside the waste pipe, a dry or faulty trap, or venting problems.
You fix it by cleaning the pipe properly and restoring the water seal — not by pouring random chemicals.
Step-by-Step Practical Fix
1. Flush the waste pipe
- Slowly pour one full kettle of boiling water down the sink
- This loosens greasy residue that traps smells
2. Deep clean the pipe
- Pour ½ cup bicarbonate of soda into the drain
- Add 1 cup white vinegar
- Cover the plug hole and wait 20–30 minutes
- Flush with another kettle of hot water
3. Clean the overflow hole
- Use a thin brush or cloth-wrapped cable tie
- Hot water + washing-up liquid
- Rinse thoroughly
4. Check the trap has water
- Look under the sink at the U or bottle trap
- If the sink isn’t used often, the trap dries out
- Run the tap for 30 seconds to refill the seal
5. Inspect the trap
- Check for cracks, loose joints, or leaks
- Smell stronger under the cabinet = faulty trap
- Replace if needed (cheap and DIY-friendly)
6. Check for venting issues
- If smell appears when toilet or another tap is used
- Or worse on windy days
- This points to poor venting — plumber required
7. Sink Gurgling When washing machine Drain
Sometime You hear gurgling when washing machine drains this issue occurred because of pipework.
What Works vs What Doesn’t
Works
- Boiling water + proper pipe cleaning
- Cleaning the overflow hole
- Ensuring the trap always holds water
- Replacing a damaged trap
Doesn’t
- Bleach alone (temporary, smell returns)
- Drain fresheners or perfumes
- Repeated chemical cleaners (damages pipes)
Quick Checklist
- Boiling water flushed slowly
- Bicarbonate + vinegar used
- Overflow hole cleaned
- Trap full of water
- No cracks or leaks
- Smell linked to other fixtures checked