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Why Does My Bathroom Sink Smell?

You walk into your bathroom one day and realize that it doesn’t smell very nice. Gathering up the cleaning supplies, you give the bathroom a good cleaning, empty the wastebaskets, mop the floor, and spray enough air freshener to nearly choke yourself.

Still, when you come back a few hours later, the unpleasant smell is back. What on earth can it be? You’ve cleaned everything in sight.

Don’t be surprised if that foul odor comes from your bathroom sink. If you’re asking yourself, “why does my bathroom sink smell?” you’re not alone. A part of your sink that’s not actually in sight—your sink drain—is often the cause of a hard-to-isolate, less-than-pleasant odor in the bathroom.

Stinky bathroom sinks can have several causes, and you can correct some of them yourself. Others will require Champion Plumbing, Bethany’s reliable plumbers, to help resolve.

What’s Causing the Odor?

Why does my bathroom sink smell? Well, there are three leading causes of smells coming from bathroom sinks: bacteria build-up, ventilation issues, and a dry P-Trap. Let’s review each of these in detail.

Bacteria Build-Up

Think about how you start most days. You head into the bathroom, grab your toothbrush and toothpaste, brush your teeth, and then spit it all out into your sink. Is there any wonder why bacteria are building up in the sink drain? And that’s just in the morning. Think of all the other waste you dispose of each day down the different drains in your bathroom.

The damp, warm darkness of sink drains represents perfect conditions for bacterial growth. Eventually, that growth can turn into black gunk called biofilm—and yes, biofilm can smell pretty bad.

The best way to determine if you have bacterial build-up in your sink drain is to unscrew your stopper to disconnect it and pull upward until it’s free from the drain. Does it have a black film covering the underside post? Then you’re operating your very own biofilm factory down in your sink drain—possibly in the pipes below your drain, also.


If the unpleasant odor you’ve detected smells like a sewer, that may be where it’s actually coming from. Everything that goes down your sink eventually winds up in the sewer, having joined up along the way with what’s going down your toilet and tub or shower drains.

Sewer smells may indicate a more severe problem. Your plumbing has vents that should be letting the sewer gas escape rather than entering your home. If you’re smelling sewer, your plumbing vents may have become clogged.

Dry P-Trap

Shaped more like a “U,” the P-trap is the curved segment of pipe you see under the sink. It’s designed to constantly hold a water barrier to protect against sewer gases from coming up through the lines and into your bathroom. If the P-trap goes dry, the barrier disappears, and the sewer gases have free rein to rise upward. The result can be a very smelly (and often very unsanitary) situation.

Even worse, P-traps are most likely to dry out when a bathroom sink gets little use, such as in a guest bathroom. The last thing you want is to have one of your guests let you know that there’s an unpleasant odor in the bathroom.

How Can I Get Rid of the Odor?

Here are some practical ways to solve the specific problems just outlined. We’ll also provide pointers on resolving other, less common causes for why your bathroom sink smells.

Removing Bacterial Build-up

To get rid of biofilm, you need to deep-clean your sink, including thoroughly scrubbing the bowl that you can see and the drain and the pipes that you can’t.

First, run hot water in the sink for a minute or two. Then, use any commercial cleaning solution designed for sinks. Scrub the sink bowl and use a bottle-cleaning brush for the drain. Scrub thoroughly and then rinse thoroughly with hot water. Repeat several times until the bottle brush comes out of the drain without any black gunk.

Plain white vinegar also works well as a cleaning solution. However, if using vinegar, make sure not to mix it with bleach or any other cleaning solution containing bleach. (When combined, vinegar and bleach create chlorine gas, which can be deadly.)

If you have an especially bad biofilm build-up, this cleaning method may not suffice. Instead, you’ll need to turn off the water source, remove the plumbing beneath your sink, and scrub each pipe individually. Again, you can use a bottle brush, but with complete access to the line, sometimes the force of an outdoor spray nozzle can do the trick on its own.

Correct Your Ventilation

In addition to a foul odor, signs of potential problems with your plumbing vents are that water takes a long time to drain or makes a gurgling sound as it goes down.

Faulty ventilation is not something you should attempt to fix on your own. Clogs in plumbing vents can release toxic gases and cause water backups that damage your home, so don’t leave them for long. If you suspect a ventilation problem, call the Champs from Champion Plumbing at (405) 544-2876.

Add Water to Your P-Trap

This solution is perhaps the easiest fix for a smelly bathroom sink. Usually, all you have to do to overcome a dry P-trap is run water down the drain for a few minutes. The water temperature doesn’t matter in this case.

You should call us at Champion Plumbing if that doesn’t solve the issue because it could mean that you’ve got a worse problem than you think or, at the very least, that your issue is not a dry P-trap.

Other Things to Check

Although the three problems described above represent the vast majority of reasons why your bathroom sink smells, there are other things you can check. If none of the above apply, look into these two before calling a plumber.

Overflow Hole

The overflow hole near the top of your sink, beneath the faucet, is also a magnet for bacterial build-up and soap scum. Use an old toothbrush to scrub the opening and then pour either white vinegar or bleach into the hole (but remember, not simultaneously).

Pipe Build-up

In addition to bacteria, other disgusting gunk that can build up includes grease, hairballs, and similar residues. Again, white vinegar and boiling water go a long way. Vinegar mixed with baking soda creates a foaming effect that can help dislodge build-up.

How Can I Avoid Future Foul Odors?

Now that you can answer the question, “why does my bathroom sink smell?” it’s time to discover how to prevent such an odor from returning. Some of these suggestions may seem obvious, but they will help you maintain a clean, fresh bathroom free of unpleasant smells:

  • Wipe down the sink regularly with pre-soaked cleaning wipes
  • Wipe the shower curtain or shower door after each use to prevent mold growth (again, pre-soaked cleaning wipes are suitable for this purpose)
  • Hang up bathtub mats so they can drain, rather than letting the water evaporate slowly, which can lead to mold growth and mildew on the underside of the mat
  • Drape damp towels across the towel rack or shower bar so they can dry more quickly
  • Add a disposable air freshener to your bathroom décor (the plug-in variety works best)
  • Use scented liners for your wastebaskets

Call the Champs in Bethany, OK

When you need a professional plumber, don’t settle for less—call the Champs! Champion Plumbing in Bethany, OK, offers a full range of plumbing services, high-quality products, and replacement parts. Whether you need professional drain cleaning or help with another type of sink, such as garbage disposal services by Champion Plumbing, call us today at (405) 889-1318.

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The next time you need a plumbing contractor, call Champion Plumbing if you’re in the Edmond, OK area at 405-342-3571 and give us the chance to earn your business.