Mold On Toilet: Here’s How To Clean & Prevent Toilet Mold & Mildew

Toilets commonly harbor large amounts of bacteria, however, under the correct circumstances toilet bowls, cisterns, and seats can also be a hotbed for mold and mildew.

So, what causes a large buildup of mold on a toilet, how can you identify it, remove it, and prevent it from happening again? In this article, we will be answering all these questions and many more, so for all you need to know about mold growing on toilets, their tanks, and their seats, keep reading.

moldy toilet

What causes mold around toilet tanks, seats, and bowls?

Mold grows in toilets because they provide the perfect environment for it to not only live but thrive.

In order for mold to live, it only needs a source of moisture and a source of nutrients. If the environment also happens to be between 60-80 degrees Fahrenheit and dark, then mold can spread even more rapidly.

In and around your toilet, there is plenty of moisture, by the way of condensed water pooling on the walls of the tank, or water evaporating from within the bowl and condensing on the lid or on the walls of the bowl, which mold can use as a source of hydration.

Nutrients can consist of any organic matter, and of course, within a toilet bowl, if not regularly cleaned, human waste acts as a source of nutrients for mold. Food sources can also come from accumulated dust that settles on the bowl in layers. This dust is mostly made up of dead skin cells and other organic particles that mold can use for sustenance.

I also stated that mold prefers dark areas with a temperate climate between 60-80 degrees Fahrenheit, and toilet tanks and bowls again provide this environment. Once the lid or cover is closed on either the toilet seat or tank, no natural sunlight ( the UV rays of which will kill mold and its spores) can come into contact with the interior of the toilet. Mold is happy to live in darkness, as it is a fungus and not a plant, therefore it can grow and spread without sunlight, as it gets its nutrients without using photosynthesis.

Which types of mildew grow on toilets?

As with the rest of the home, the three most common strains of mold you are most likely to find growing around a toilet are Penicillium, Aspergillus, and Cladosporium.

These mold strains each have distinctive textures, markings, and colorations which can help to identify which strain you may be dealing with. Even with distinctive patterns, many molds can be mistaken for each other, therefore, if you want to be absolutely certain of which strain has taken a liking to your toilet, it may be best to purchase a home mold testing kit. You simply take a sample, send it to a lab and you will usually have the results in a few days to a week.

Here are the most common traits of each strain listed above to help you try to identify which strain of mold you are dealing with.


Cladosporium strains of mold are typically seen in dark colorations, such as brown, black-brown, and gray-green with a texture likened to velvet or powder.


Aspergillus strains of mold typically begin in white or light colors but turn to darker shades such as browns, dark greens, or pale yellows, usually with a cotton-like texture.


Finally, Penicillium strains of mold will more often than not be found in slightly lighter colors, including, gray, green, green-blue, yellow, or yellow-green, and again, appear with a powdery or velvet-like texture.

Is the fungus dangerous?

Yes, Aspergillus, Cladosporium, and Penicillium strains of mold all have the ability to produce mycotoxins, which can cause allergic reactions and serious health complaints in those sensitive to them.

If these mold strains are allowed to grow into sizeable colonies, a large number of spores can be released into the air where they can be inhaled or ingested.

In large enough quantities or over prolonged periods of time, mycotoxin exposure can cause health conditions even in those not sensitive or allergic to them.

The most common symptoms of mycotoxin and mold exposure are:

  • Breathlessness
  • Fatigue (In rare cases)
  • Dry skin
  • Skin irritation
  • Coughing

As mold tends to release mycotoxin-laden spores as a defense mechanism whenever they feel threatened, it is important that you wear the appropriate safety equipment for trying to deal with mold removal in a toilet of your own to avoid coming into direct contact with the mold or its spores (more on this later in the article).

How to identify toilet mold

It can be difficult to identify which specific strain of mold you are dealing with on or in a toilet, as the colonies are often too small to see much detail. However, there are a few telltale signs that what you are looking at is indeed mold, and not water lines or general stains.

When mold grows within a toilet, it grows in black, brown, green, or other color variations in rings. More often than not, you will find these rings just above the water line in the toilet bowl, around the rim of the toilet bowl, around the inner circle of the underside of a toilet seat, above the water line in toilet tanks, or on the lid of the cistern where water can condensate.

Clusters of mold are often made up of many smaller specs that have clumped together, but you may also see smaller, individual small patches of mold.

How to clean a moldy toilet bowl

The good news is, that even though cleaning mold off a toilet may not be the most luxurious way to spend an afternoon, it isn’t a particularly difficult task. Before you begin cleaning mold, there are a few important safety factors that need to be taken into consideration.

Safety precautions

As we have stated, mold can be hazardous to your health, and some of the cleaning methods we are about to suggest involve you getting close to the mold. Because of this, we heavily recommend you wear protective gear to avoid either inhaling or coming into direct contact with mold or spores.

We recommend a good quality breathing mask to prevent inhalation, goggles to stop mold spores from coming into contact with your eyes, and rubber gloves to avoid skin irritation, again from direct contact (and for general hygiene).

What you’ll need

Before we begin, here is a quick checklist of the items you are likely to need.

  • Vinegar (method 1)
  • Soft-bristled brush
  • Vinegar and Baking powder (method 2)
  • Hydrogen peroxide (method 3)
  • Steam cleaner (method 4)
  • Dry cloth (method 4+5)
  • Detergent (method 5)
  • Sponge (method 5)
  • Spray bottle

The Vinegar Method

Vinegar is an excellent, natural method to kill mold, and it works very well on the kind of mold that you find growing on toilets. The acidity level is high enough to kill the mold without being potent enough to damage either the enamel or any of the plastic or rubber components within the tank.

To use vinegar to kill mold on the toilet seats, bowls, and tanks, use the following steps:

Step 1. Make a white vinegar solution by adding four cups of water to one cup of white (distilled) vinegar.

Step 2. Apply the vinegar solution directly onto the mold. Make sure you also apply the solution to the entirety of the toilet, as mold spores could have spread to other areas, and will quickly regrow if not killed.

Step 3. Leave the vinegar solution to work for at least 1 hour, then scrub the affected area with a soft-bristled brush. The toilet brush should be totally fine for this job as it’s made to not damage the bowl.

Make sure you get deep within each part of the toilet, including high up into the rim of the toilet. Should any mold patches be missed, they will quickly begin to spread again in only a few days.

Step 4. Flush the toilet to remove any of the dislodged and dead mold. If required, repeat the steps again until all mold is removed.

Vinegar and baking soda method

Whilst vinegar is an excellent method to kill mold, in certain circumstances, it might not be quite powerful enough to complete the job.

So, to remove really stubborn mold and its associated stains, use baking powder and soda mixed together.

The benefit of this method is that the vinegar and baking powder both kill the mold in different ways, doubling its efficacy, whilst the oxidizing effect of mixing the powder with vinegar helps to get underneath and lift mold and stains.

To use baking powder and vinegar to remove mold from a toilet, use the following steps:

Step 1. Measure out one cup of undiluted vinegar and a tablespoon of baking powder.

Step 2. Apply undiluted vinegar to the visible mold patches and sprinkle on some of the baking powder.

Step 3. Allow the vinegar and powder solution to stop fizzing and leave for another ten to fifteen minutes.

Step 4. Using a soft-bristled brush, scrub the areas where the solution was placed to remove the now-dead mold.

Step 5. Using a clean, damp cloth, wipe away any mold and baking soda residue.

Hydrogen peroxide method

Hydrogen peroxide is a powerful oxidizer with antiseptic properties. It is for these reasons that it can be a highly effective way to kill and remove toilet mold.

To use hydrogen peroxide to remove mold from a toilet, use the following method:

Step 1. Measure out a cup of hydrogen peroxide and pour it directly over the affected areas. If the bowl is badly affected, you can also pour a cup of hydrogen peroxide directly into the toilet water.

Ensure the hydrogen peroxide is completely covering all the affected areas, so if required, apply to tricky areas (such as under the rim) using a spray bottle.

Hydrogen peroxide will not damage parts in your toilet cistern, so, feel free to pour a cup into the tank if this is where the majority of your mold problem lies.

Step 2. Leave the hydrogen peroxide to work for twenty minutes, this should be plenty of time for the chemical to effectively kill the mold and any bacteria that may be lurking.

Step 3. Using a soft-bristled brush, scrub all the areas you applied the hydrogen peroxide. Should you find the mold is still not coming away from the toilet easily, apply another coating of hydrogen peroxide and wait a further twenty minutes before repeating the process.

If you’ve added a cup of hydrogen peroxide into your toilet tank, you can flush this through after twenty minutes. This should be long enough for it to have killed the majority of the mold.

Steam cleaner method

Steam cleaners heat water past the point of boiling and pass the steam out under high pressure through a nozzle at the front. This steam reaches temperatures of 325 degrees Fahrenheit, hot enough to kill bacteria, dust mites, and toilet mold.

The steps for using a steam cleaner to remove mold from your toilet are fairly simple, however, it is important that you wear safety equipment (including eye and hand protection) whilst using a steam cleaner, due to the high temperatures involved.

To use a steam cleaner to remove mold from a toilet, use the following steps:

Step 1. Using a high-pressure nozzle, steam not only the obviously affected areas of the toilet but get into all the hard-to-reach areas, such as high up under the rim of the toilet and behind the back of the working parts in the tank.

Step 2. For really stubborn mold, you can add a small amount of vinegar to the water reservoir. This will assist in killing mold and lifting some of the heavier stains.

Step 3. Using a dry cloth, wipe over any of the areas you cleaned where water has pooled. The high temperatures of the steam mean that the vast majority will simply evaporate, but some small pockets of water may remain.

If you’d like to use the method above, and you’re in need of a steam cleaner, I’ve placed a few links below to the Amazon store to some of their most highly rated (and affordable) steam cleaning units.

Secura Steam Mop 10-in-1 Convenient Detachable Steam CleanerOpens in a new tab. (US)

Portable Handheld Steam CleanerOpens in a new tab. (UK)

Detergent method

One last method to clean mold from a toilet is to use simple, old-fashioned detergent (preferably anti-bacterial).

As you will again be getting close to the mold in this method, eye protection, rubber gloves, and a breathing mask are recommended.

To use detergent to clean toilet bowls, tanks, and lids, use the following steps.

Step 1. Create a solution using warm water and detergent. Mix well until the detergent creates a lather.

Step 2. Dip an abrasive sponge into your detergent solution, and using the abrasive side, begin to scrub the mold after the area using circular motions.

Step 3. If after scrubbing some mold patches remain, drizzle some detergent directly onto the patch and leave it to work for 10-15 minutes, before attempting to scrub the mold away again.

Remember to get into every area where mold could be hiding, including high up in the rim of the bowl, the underside of the seat, and past the working parts in the tank (if you can reach it). This will remove any mold that’s out of direct sight and will prevent it from re-establishing a colony.

Step 4. Using a clean and dry cloth, wipe over the areas that you have cleaned to ensure there is no mold or dirt residue.

How to prevent mold in a toilet

Prevention is always the best cure, and as tackling mold buildup in a toilet can be an unpleasant thing to have to do, you are certainly better off preventing its occurrence in the first place.

Fortunately, preventing mold from accumulating on a toilet is fairly easy, there are just a few measures to take, which are:

Keep it clean

Cleaning your toilet at least once per month is an effective way to remove bacteria and prevent mold from gathering and establishing a colony.

A deep clean is not required on a monthly basis, but scrubbing the hard-to-reach areas in the tank and under the rim of the toilet as well as the bowl and seat is a good way to prevent the accumulation of mold.

Standard bleach can also be poured into the bowl and under the rim each week as a prevention method.

Keep it dry

Your toilet will always have a certain level of moisture, as it contains water, but after it has been cleaned, try to ensure any small pools of water are dried to prevent mold from using them as a source of moisture.

A toilet tank is also very prone to condensation, as the internal temperature of the tank is lower than the external temperature of the bathroom or WC. This causes water to condensate on the surface of the cistern, known as “toilet sweating”. Insulating the tank, installing an extractor fan, and fitting an anti-sweat valve are all viable options to reduce water condensing and pooling.

Keep it ventilated

Mold hates frequent airflow, as it makes it difficult to settle in one place and establish a colony. This is why you often find mold growing in sheltered areas of a property with little airflow, such as a basement.

You can increase the airflow of your bathroom by installing an extractor fan, air vents and by simply leaving the door open for longer periods. If you plan on leaving your property for several weeks, consider leaving the toilet seat up and the bathroom door open to allow at least some fresh air and sunlight to enter the room.

Extractor fans are a very effective method, as they not only remove moisture created whilst bathing but as they expel the air from the room, new air is pulled in, creating airflow.


Why is there mold on your toilet seat?

Mold typically grows on the underside of a toilet seat due to high humidity levels within the toilet itself, especially when the lid is closed for long periods and there is a lack of regular cleaning.

Can urine cause mold on a toilet seat?

Absolutely, urine left on a toilet seat and not cleaned will provide both nutrients and moisture for mold to live off. Any urine or feces that are not cleaned thoroughly off a toilet seat will provide the nutrients required for mold growth, and when combined with high humidity levels within the toilet, they provide the perfect environment for its development.

What does black mold in a toilet mean?

You may have heard that finding black mold growing in your toilet bowl could be a sign that you or someone in your household has diabetes.

The idea behind this is that there would be a greater amount of sugar excreted from a person affected with diabetes, which would provide nutrients for mold to use for sustenance.

The good news is that this is not scientifically backed, and is currently no connection with black mold growth in a toilet bowl being a sign of diabetes. It is more likely due to a lack of cleaning and high moisture levels.

Is it ok to put bleach in your toilet tank?

You may have noticed that the tips we provided on cleaning mold or mildew off a toilet earlier did not make mention using bleach within the tank.

This is because bleach will be fine within the toilet bowl and around the rims of the, however, it should never be used within the tank, as it can damage plastic parts, rubber seals and corrode metal parts.

When to hire a professional

In most cases, you should be fine to remove mold from your own toilet without requiring help from a professional.

When you might need to hire someone, is if you find the toilet very quickly becomes moldy again after being cleaned. This could signal that the issue may not be with the toilet as such, but more with the environment itself.

There is a good chance that you may be dealing with an undiagnosed mold infestation within your bathroom or property if your toilet quickly becomes moldy each time you clean it.

In this scenario, it would be prudent to hire a mold remediation expert, as they would be able to conduct efficient testing and diagnostics of the property, whilst assessing how the problem could be eradicated.


Finding mold and mildew on toilets is not uncommon, as the perfect combination of nutrients from urine and feces combined with moisture from within the toilet and humid bathrooms provide the perfect environment for mold growth.

The mold can be removed easily, (with several options listed within this article), but prevention is preferable and luckily, also very simple.

Chris Walker

Chris Walker has struggled for several years with mold after buying his own property. After finding the solutions to several issues around his home, he decided to create this site in order to answer as many questions about mold and mildew as possible to help others dealing with the same problems.

Recent Posts