How to Do It (Takes Less Than 2 Minutes)
This is important: oil alone won’t help if the trap is already dry.
Do this first:
- Pour a bucket or large pitcher of water down the drain.
- This refills the P-trap completely.
Then add the oil:
- Pour about 1 teaspoon of cooking oil per inch of pipe diameter.
- For most household drains, 1–2 teaspoons is enough.
- Any standard cooking oil works (vegetable, canola, olive).
The oil floats on top of the water, creating a seal that dramatically slows evaporation.
You don’t need to repeat this often—only when the drain goes unused for long periods.
What Not to Do
- Don’t pour oil into drains that are used daily.
- Don’t use grease or solid fats that can harden.
- Don’t skip the water step—oil alone won’t block gas.
When to Look Deeper
This trick solves dry trap odors—not every plumbing issue.
If smells persist after refilling and sealing the trap, consider professional help if:
- The odor is constant and very strong
- You notice gurgling or slow drainage
- There’s visible sewage backup
The Takeaway
Most drain odors aren’t caused by something broken.
They’re caused by something missing: water.
A thin layer of cooking oil can quietly protect unused drains for months, keeping sewer gases out of your home with almost zero effort.
It’s one of those rare home fixes that’s cheap, fast, and actually works.
