Why Does My Bathroom Sink Drain Smell? 5 Causes and How to Solve Them

You’ve scrubbed the shower and taken out the bathroom trash, but something still doesn’t smell quite right in your bathroom. Unfortunately, bathroom odors can sometimes sneak up through the drains, leaving you wondering why your bathroom sink drain smells and how to fix it. If you’re tired of wondering why your bathroom sink smells, read about five common reasons for bathroom sink drain smells and how to solve them.

1. Dry P-Trap 

The P-trap, a set of pipes shaped like a “U” often found beneath sinks, is responsible for keeping sewage smells away from the house and preventing pests from coming inside. The P-trap, also known as the U-bend, holds water. However, a P-trap can leak gas smells into the bathroom when dry. This may happen because it is clogged, the hot weather evaporates the water in the pipes, or the sink hasn’t been used in a long time.

Solution

When it comes to sewage gases, you’ll need to hire a drain cleaner near you to help fix the dry P-trap as soon as possible. Aside from the unpleasant smells, long-term sewage gas exposure can cause health problems like headaches and dizziness, according to the International Association of Certified Home Inspectors®.

2. Soap and Hair Buildup

Bathroom sink drains collect a lot of organic matter, from toothpaste and hand soap to hair and shaving cream. While much of this may wash down the drain with ease, some of it is bound to cling to the sides of the pipes. As more and more soap, hair, and other products collect, they can start to smell.

Solution

You can try a small plumbing snake or store-bought drain cleaner, following the instructions on the label to clear the debris buildup. For a homemade cleaner, you can pour in baking soda followed by distilled white vinegar. As these two ingredients react, they will loosen the soap, hair, and other buildup from the pipes.

3. Deep Clog in the Sewer Line

Sometimes, soap and hair buildup can become too much, pushing farther and farther down the pipes until they create a much bigger clog you can’t reach with a little manual snake and some baking soda. The clogged materials themselves may smell, but they can also create a gas leak from the P-trap that will smell. 

Solution

For deeper clogs or problems with the sewer line, you’ll need to call a drain cleaning pro. These experts have the right tools to safely find and solve sewer line problems without risking damage to the pipes.

4. Growing Mold or Mildew

Bathrooms can be notorious for mold and mildew growth. The warm, humid environment provides ideal growing conditions for mold and mildew, which can start to smell as they accumulate. While you may be able to spy growth in the shower and tackle it quickly, you’re less likely to notice these issues when they are in the sink drain.

Solution

Similar to handling surface-level clogs (and their accompanying odors) in the bathroom sink drain, you can eliminate mold and mildew by sprinkling baking soda and distilled white vinegar into the drain. Then, follow it up with hot water, wait about five minutes, and flush the pipes with cool water.

5. Plumbing Ventilation Issue

Your home’s plumbing system needs proper ventilation to release those smelly sewage gases. These vents run all the way up to the roof to release gases, but this location also can leave them open to clogs from outdoor debris, like leaves and sticks. If the plumbing vents are obstructed, they could send those smells back into the home, causing bathroom sink drain smells.

Solution

Working on the roof for any reason can be dangerous, so it’s best to call a plumber to look at the plumbing vents and unclog them if needed.

How to Prevent Smelly Bathroom Drains

There’s never a good time to notice bathroom sink drain smells, but it can be especially frustrating when you have guests on their way or a busy day and no time to find out what’s wrong. Luckily, with a few simple upkeep tasks, you can minimize the risk of smelly sink drains.

Clean the Drain Weekly

Instead of waiting until there’s a clog to use drain cleaner, clean a smelly drain and pipes about once a week to clear out the organic matter before it starts building up. You can use a store-bought cleaner or the baking soda and vinegar combo to keep smelly clogs at bay.

Keep the Sink Clean Daily

Similarly, keeping the bathroom sink clean can also help remove debris before it can wash down the drain. Wipe down the sink with a cleaning cloth and your favorite cleaner daily or at least a few times a week.

Flush Water Down the Pipes Often

One common problem for P-trap leaks is that they don’t get used enough, particularly for guest bathrooms or other bathrooms that aren’t used daily. Every two or three weeks, make sure to run water through the drains in sinks that aren’t used regularly.

Check the U-Bend

Blockages commonly occur in the U-bend, also known as the P-trap, which can create odors. Use a flashlight to check it for any blockages or debris buildup at least once per month. If you notice any residue, you can pour a 1/2 cup of baking soda down the drain, followed by 1 cup of white vinegar. Let the solution sit and bubble for a few minutes before flushing it with hot water. 

Additional Tips to Keep Your Bathroom From Smelling 

A smelly bathroom sink drain is a homeowner’s right of passage. If you use a bathroom long enough, you'll run into an olfactory issue, however minor. The truth is bathrooms can stink for reasons outside of plumbing problems. Luckily, there’s something you can do about it. Follow these tips to keep your bathroom smelling fresh.

Dry Towels and Bathmats Properly 

Towels and bathmats keep you and your bathroom dry but retain moisture. This creates a perfect storm for mold and mildew, which can lead to a noticeable stink. To beat the stench, hang up towels after each use and drape wet mats over your tub to help them dry much faster.

Clean Your Shower Door or Curtain Regularly 

Is there a weird smell wafting from your shower? You may want to roll up your sleeves if you haven’t cleaned it in a while. Stinky mold and mildew can cling to surfaces like your shower curtain or door.

Use Scented Trash Bags 

Trash can occasionally get stinky, but a scented trash bag can help mask any unwanted scents. This includes unrelated smells like stinky drains or old laundry you should probably throw into the wash.

Use Candles or Wall Plug-Ins 

Scented candles and wall plug-ins can’t erase the source of a bad smell, but they can cover it up temporarily. If you don’t have ventilation in your bathroom, a small scented candle can help kick the smell of excess moisture and regular bathroom use. 

How Do You Clean a Smelly Drain? 

There are a few different ways you can clean a smelly drain. The best method depends on the source of the smell. If it’s a clog, you’ll need to clear the clog. If not, you can use one of these simple methods:

• Boiling water: Some homeowners pour boiling water down the drain to help clear out mold, mildew, and smelly biofilm. Keep in mind that not all pipes can withstand such high temperatures. You may have to let the water cool a little before using it, especially if you have PVC pipes.

• Baking soda: Sprinkle some baking soda in and around your drain, let it sit for about 15 minutes, and then scrub it away.

• Vinegar: Mix 1 part baking soda and 2 parts vinegar, then slowly pour it down the drain. Vinegar is acidic, so as an added bonus, it helps kill bacteria and remove limescale. 

Though you might be tempted, resist the urge to pour bleach down your drain as a quick fix. It won’t help clear a blockage and could damage your pipes. If your drain smells, you can clean around the drain and the rest of the sink with diluted bleach, but don’t pour it down the drain. If the issue persists, bring in a pro.

Should You Contact a Pro?

Handy homeowners can fix bathroom sink odors, like minor blockages. You may be able to turn off the water under the sink and make small repairs (like fixing a leaky faucet that’s feeding mildew with a constant drip). But when it comes to more complex or dangerous issues, like plumbing ventilation problems or gas leaks, hire a local sink repair service with the tools, skills, and experience to fix it safely.