Shower Drain Smells Like Mildew: Causes & Fixes

The shower drain can have all sorts of disgusting smells. From a musty scent to that of rotten eggs, stale and stagnant water, or even accumulated soap scum. The most prevalent smell is the musty type, also known as a mildew odor.

A mildew-like scent is a clear indication of the growth of mold and mildew in your shower drain. The drainage system offers conducive warm and wet conditions, which then allows for great breeding grounds for mildew and mold. The first thing you should do is fix the drain as soon as you notice it because it can easily spread throughout the home.

An easy fix is pouring bleach or a mixture of vinegar and baking soda in the drain, followed by boiling water. The mildew along with the smell clears right off. For a more in-depth look into this, other causes and fixes for mildew-like smells in your shower drain, do keep reading.

Why is there a Mildew Smell?

The drain would only smell of mildew if there is actual mold or mildew growing in your shower drain. This unpleasant smell could also be present in your bathroom sink, tub, or an adjacent toilet. This only goes to show the growth of mildew has increased and will continue to spread rapidly.

Mildew bathroorm

The musty/mildew scent is very common in homes so you shouldn’t be alarmed. However, it also goes to show that there’s is an issue with your drainage system that needs a quick and effective solution.

Of course, the process of cleaning out will begin with checking for blockages in the drain that caused there to be conducive breeding grounds for mold and mildew. After this, a cleaning and clearing process shall follow.

Causes of a Musty/ Mildew Smell

You already know the most obvious reason why your drain smells musty. However, there could be other reasons for the mildew-like scent. They include;

  • Clogged drains – this is an early sign that mildew will eventually grow. A blocked pipe leads to a contaminated drain with the best growth conditions for mold and mildew spores. If the damp conditions aren’t dealt with soon enough, you will see the mold appear sooner rather than later.
  • Mildew in the plumbing system – mold may not be present in the immediate drain where the scent is emitting from, nonetheless, this doesn’t mean there isn’t mold growing somewhere. In the search for the smell, it’s a good idea to also check the plumbing system.
  • Biofilm – the build up of biofilm in the shower drain can also lead to a musty scent and other unpleasant odors. Biofilm may be growing inside the drain and it needs to be cleaned out, fast.

These are the most common causes of mildew-like scents in your shower drain. Before, moving to the next section, let’s first understand what’s biofilm…

Biofilm is a glue-like substance similar to grime and muck that can easily be missed for mold. Instead, biofilm is a dynamic substance of bacteria and bacterial waste that accumulates in drains and pipes after a long period of no cleaning.

The bacterial film is slimy to the touch and will also cling onto wet surfaces like the shower drains, pipes, and even walls in extreme cases.

There are multiple types of biofilm including the pink mold, which is the most prevalent. Because biofilm is an accumulation of bacteria, pink mold (Serratia marcescens) is the most likely cause.

Just like mold and mildew, the biofilm has to be cleaned out immediately, not only because you want to get rid of the scent, but also because of the possibility of multiple health problems.

Shower Drain Fixes
Shower Drain

How to Get Rid of the Smell

Now that you have identified the cause of the scent, let’s get into the fixes. Getting rid of the scent can be done in various ways. But first, you have to clear any blockages, obstructions, or clogs.

Using a toilet plunger or a drain snake to get rid of any obstructions in the shower drain. Fill up water in the shower and plunge or use the auger to either remove or push away the dirt, that way you can see inside the drain to ensure it’s clear.

The snake drain will require you to insert the auger into the drain and push it in as you crank the handle. Once you encounter any resistance, push or pull it.

Once you don’t feel a resistance anymore, remove the snake and run some water to ensure it’s clean. Now we can move to get rid of the nasty musty scent in your shower drain. Here’s a step by step guide you can follow.

Step 1: Scout the Area Infested with Mold

According to EPA guidelines, you’re only allowed to clean out the area personally if the area infested is less than 10 square feet. This is because mold occurs under a metabolic process where active mold spores release tiny puffs of gas that could be very dangerous to your health once inhaled. An area larger than 10sq feet means a professional has to get involved.

Otherwise, you can move ahead with cleaning the area yourself.

Step 2: Gather the Needed Materials

To clean out the drain, you will need;

  1. Hot water
  2. Baking soda
  3. White or apple cider vinegar
  4. Gloves and other protective gear
  5. A small brush

Step 3: Scrape Off Noticeable Mold and Mildew

As mentioned above, if it smells like mildew, it’s probably mildew. So use the small brush to scrape the inside and top of the shower drain. You could see black or brown spores in the drain, that’s what you need to be scraping off.

Also, you could see orange or pink stains, this means you’re dealing with pink mold or what’s commonly referred to as S. marcescens.

Because mold in general is dangerous to deal with, ensure you keep yourself safe by covering up with gloves on your hands, probably some goggles, and a mask to avoid inhaling any dangerous games.

If your drain so has biofilm, use the brush to break off its slimy film before you pour any antimicrobial disinfectant. Check the walls as well for any mold or biofilm as it could have easily spread to those areas as well. Do this step until you can see any more biofilm or mold.

Step 4: Create and Use the Disinfecting Paste

Mix one part baking soda with one part vinegar to form a paste. If the area of infestation is large, mix some more solution, just let them be equal parts of each. Once the paste is made, apply in the drain and over the drain up to the adjacent wall. You can use a brush to apply and spread the paste all over.

Let it sit for ten to 30 minutes so as to loosen dirt and the remaining mold. After that, use the brush to gently scrub the shower drain and the walls. Repeat this process until you’re satisfied with how it looks.

Step 5: Final Rinse

After scrubbing, you need to do a final rinse with vinegar and hot water. First, sprinkle about two tablespoons of baking soda into the drain again. Pour over the vinegar to initiate a fizzing sound. Cover it up for as long as the drain is still fizzing. As that is going on, boil three liters of water.

Note: only boil to about 150° Fahrenheit because PVC piping can’t withstand as high temperature as above 200 °Fahrenheit which could damage the pipe entirely. The above temperature should be enough to kill any remaining mold. Because baking soda and vinegar are anti-fungal, this solution ought to work. Moreover, the hot water will also clear any build up in the drain.

After this process, the scent should be long gone by now. But if the scent is recurring, you could be having an even bigger mold problem than you anticipated. In such a case, you need to consult with an expert to guide you on the best way to permanently get rid of the mildew smell.

Step 6: Use Alternative Solutions

In case you don’t have the supplies above, you can simply use bleach. Store-bought or homemade bleach has the acidic properties of vinegar which can therefore act as an alternative solution to removing the musty smell in your shower drain. Bleach is an industrial mold killer and will surely kill any bacteria in your drain as well.

Here’s how to use bleach to get rid of the mildew smell in your shower drain.

  1. Pour about two cups of bleach down the shower drain and let sit for an hour or so.
  2. Follow up with three liters of boiling water.
  3. Repeat as many times as you want.

Tips to Prevent the Smell in the Future

Follow these great tips to prevent the musty smell in the future.

  • Ensure you regularly clean the shower and use bleach to disinfect and kill germs, mold, and mildew in the shower drain.
  • Keep the walls and floor of the bathroom dry at all times to avoid creating a good breeding ground for mold and mildew.
  • Always inspect your bathroom piping systems to check for any water leaks. Leaks encourage a damp environment which is not advisable for keeping off the mold.
  • Ventilate the bathroom around the clock. Either by opening the windows or using a fan/ air conditioner.
  • If your shower has grout, regrout the areas that have loose or broken tiles and spaces. This way, water will not be sitting there all the time.

Mold and mildew can easily grow from anywhere. They only need a good breeding ground which involves water or a damp area. Your best chance of preventing them is to keep the bathroom area as dry as possible.

Maintain regular cleaning to prevent any regrowth and always follow up with an expert if you suspect extended mold infestation. This way, they can check your piping all the way to your septic tank to avoid it moving to other rooms in the house.

Further Reading: Toilet & Bathroom Odor

Other Shower Drain Issues and Fixes

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