Reasons Why Your Bathroom P-Trap Smells (& How To Clean It)

A bathroom that smells like a forgotten science experiment is never a good sign, and one common source of this foul odor is your sink's P-trap. The P-trap is the curved pipe under your sink designed to hold water and prevent sewer gases from entering your home. However, when things go wrong with this u-shaped pipe, you might notice unpleasant odors creeping into your bathroom.

One common reason for a smelly P-trap is that it's dry. The water in the pipe's bend creates a barrier that blocks sewer gases from rising up. But, if the tap dries out, those gases can escape into your bathroom, causing a nasty odor. This usually occurs when a sink hasn't been used for a while, allowing the water to evaporate, or if you have a leak. Check for excess water or damage on the floor that might indicate a leak. 

Another cause could be a buildup of debris inside the P-trap. Over time, soap scum, hair, and other particles can accumulate. This buildup can cause blockages or decompose, leading to unpleasant smells. Lastly, there could be a problem with the vent lines, which help regulate pressure in the pipes. If a vent line is damaged or blocked, gases from the sewer might leak through, even if water is present in the trap.

To deodorize a sink you don't use often, run water through it every few days. Also, pouring a cup of either baking soda or vinegar down the drain every few weeks can help neutralize any potential odors before they start. If you use vinegar, let it sit for about an hour, then rinse with hot water. Baking soda can be flushed right away with hot water.

If your bathroom sink continues to smell badly, cleaning the P-trap is almost always the solution. To do this, start by turning off the water supply and placing a bucket under the pipe to catch any water that spills out. Then, unscrew the slip nuts on either side of the P-trap. Carefully remove it and pour out the water. You'll likely find some debris inside the trap, so use an old toothbrush or wire brush to scrub it clean. If the build-up is significant, soak the trap in warm water and vinegar to loosen any stubborn dirt.

Once the P-trap is clean, reattach it and run water through the sink for a few minutes. This should seal the trap and prevent sewer gases from coming through. If the odor persists, check for any signs of water leaking or other issues that might need professional attention.