Shower Drain Smells Like Mildew

A musty or mildew-like smell from your shower drain or bathroom sink is a sign of mold or mildew.

The warm and wet conditions in most drainage systems in the home provide the best breeding grounds for mold and mildew. 

If you don’t get rid of mold in your bathroom, it could easily spread to the rest of the home and cause health problems. A shower drain that smells like mildew has mildew and mold growing under the drain cover.

The best way to get rid of the musty smell is to pour baking soda into the drain, followed by white vinegar and then boiling water. This will kill the mildew and eliminate the musty smell as well.

The constant damp conditions in the shower drain, coupled with the dirt that serves as nutrients, provide the best conditions for mold and mildew to grow within the drain.

These microorganisms emit a musty or mildew-like smell that increases with time. Clearing out the mold requires using a mix of baking soda and vinegar, or bleach and white vinegar. Be aware, that ants are also attracted to mildew.

Causes Of A Musty Smell from The Shower Drain

A normal and well-maintained shower drain doesn’t have any unpleasant smell. In fact, it shouldn’t have any smell at all.

The musty smell is a sign that there is a problem with the drainage system.

You’ll need to also check for any blockages to the drain since these are the best breeding grounds for black mold and mildew.

While the clearing process takes a few minutes, proper cleaning should be done on a frequent basis to prevent the regrowth of mold and mildew. The issue can be just within the drain hole itself, or the entire system down to the septic tank.

The causes of the musty smell include:


A blocked or clogged shower drain provides the best growth conditions for mold and mildew spores. The dirt from the soap and the constantly damp conditions from the use of the shower are thus the cause of this smell.

If not eliminated early enough, the mold and mildew will easily spread to the rest of the bathroom.


When mold and mildew find their way into the plumbing system, the musty smell will still emerge from the drain and other outlets.

The issue may be that there is a blockage within the piping system or other areas where the water pressure is low and the mold and mildew spores can attach themselves and grow.

This cause is far more common than having a clogged drain. We did a video on PEX plumbing for showers that usually are less prone to mildew and mold.

How To Get Rid of a Mildew Smell in The Shower Drain

Shower drain smell like sewer

With the causes stated above, the solution lies in killing the mildew or mold from within the drain or the piping system. For this exercise, you’ll need the following items: baking soda, white vinegar, plumbing snake or plunger, and hot water.

Here’s how to get rid of the mildew smell in your shower drain:

  1. Remove the drain cover and any visible blockages.
  2. Clean the drain cover to get rid of any mold and dirt.
  3. Use the plumbing snake or plunger to unblock the drain if blocked.
  4. Pour ¾ of a cup of baking soda into the drain.
  5. Add ½ of white vinegar into the drain then cover it for between 15 to 30 minutes (or until the fizzing stops).
  6. Pour about 3 liters of boiling water into the drain.

This procedure works well given that both white vinegar and baking soda are natural anti-fungal remedies. These, combined with the hot water, help kill the mold and mildew both within the drain and in the piping system.

The hot water also prevents the buildup of soap within the drain. Soap is among the reasons for drain blockages and other unpleasant odors.

If this method doesn’t work or the smell resurfaces after a while, you’ll need to call in a mold expert who will identify the exact source of the mold and permanently get rid of it.

Use Bleach to Remove the Musty Smell

An alternative solution to removing the musty smell in your shower drain is using household bleach.

It is the most common mold killer, and it is found in many commercial mold killers. Other than killing mold, it will kill bacteria in your bathroom – common for causing a sewer-like rotten egg smell.

Here’s how to get rid of the unpleasant mildew smell from your shower drain using bleach:

  1. Pour half a cup of bleach down your shower drain and leave it for an hour.
  2. Pour plenty of hot water into the shower drain.
  3. Sprinkle borax or baking soda into the drain to kill and prevent mold.
  4. Pour a cup of white vinegar into the drain and wait until fizzing stops.
  5. Wait a few minutes and then pour some more hot water into the drain.

The fizzing usually comes from baking soda reacting with vinegar, so it shouldn’t worry you. However, you should note that extremely hot water can damage any plastic plumbing in your bathroom,

The bleach, baking soda, and hot water will get rid of the mildew smell in your shower and bathroom. It will kill any mold off. If you see any moldy surface, apply the same treatment to prevent any unpleasant odors thereafter.

How To Prevent the Musty Smell

Once you’ve cleaned the drain or other areas, you should focus on keeping the home free from mold. You can do so by frequently carrying out the procedure above to kill any germinating mold and mildew spores.

Other preventive measures to take include the following:

  • Keep the walls and floor of the bathroom dry after using it.
  • Eliminate all water leakages from the bathroom and piping system.
  • Ventilate the bathroom with a fan or by opening the windows at all times.
  • Regrouting areas in your shower where the grout is loose or replacing broken tiles also eliminates the areas where mold and mildew can grow.

With mold and mildew, keeping the home dry is the best chance you have at preventing and eliminating them. This way, you can be sure of doing away with the mildew or musty smell.