Ever walk into a guest bathroom, laundry room, or utility space you rarely use and notice a faint sewer smell? You’re not imagining it — and the cause is often surprisingly simple.
Under every sink and floor drain is a U-shaped pipe called a P-trap. Its job is to hold a small amount of water that creates a seal, blocking sewer gases from entering your home. When a drain isn’t used for a while, that water can slowly evaporate. Once the seal breaks, odors can travel right back into the room.
The Simple Fix (Try This First!)
In many cases, the solution is quick and easy.
✔ Refill the trap
Slowly pour about a quart of water down the unused drain. This refills the P-trap and restores the water seal that blocks sewer gases.
✔ Slow down evaporation
For floor drains, adding a tablespoon of cooking oil after the water can help slow future evaporation by creating a thin barrier on top of the water.
Give it an hour or two after refilling the trap. In most cases, the smell should disappear once the seal is restored.
When to Call a Professional
If the odor returns or never fully goes away, the issue may be more than a dry trap. Persistent sewer smells can indicate:
✔ A blocked or improperly vented drain
✔ A cracked or leaking drain line
✔ A loose or failing connection under the sink
✔ A deeper plumbing issue allowing sewer gas to escape
These problems require proper diagnosis to fix safely and permanently.
At Plumberoo, we believe in honest solutions. Gary will identify the real source of the smell and explain what’s happening — without guesswork or unnecessary repairs.
Tried the simple fix and still noticing an odor? Don’t live with it.
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If you have a plumbing problem and don’t know what to do… CALL PLUMBEROO!
817-766-6000
