What Causes Black Mold In A Toilet | Get the Proper Ideas

Are you having trouble dealing with black molds in your toilet? Are you wondering what are the causes of black mold in your toilet? Having molds in your toilet can be frustrating but there are ways of killing mold. Well, even if you clean your toilet regularly, there are chances of mold developing.

What cause black mold to develop in your toilet? There are so many causes of black molds in your toilet. Mold spores develop in dark and damp places like the toilet. However, you might find that some toilets get more molds than others depending on the calcium deposit in your water.

Some people also say that if your body has a high level of glucose as a result of diabetes, your excretion can cause the development of more molds in the toilet. Black mold in toilet bowl for people with diabetes is very common.

I made this comprehensive guide to provide you with more information about black mold, its cause, and prevention and how to get rid of it.

Black mold is a type of fungus that has a dark green or black look. This type of mold appears in moist environments like baths, toilets, showers, basements and kitchens just to mention a few. You can also find the mold on dirt, paper or wood.

Majority of black mold are toxigenic meaning that they produce toxins that can be irritating or affect people who have pre-existing conditions. They produce mycotoxins which are produced as mold spores and they eat and grow as well as form colonies with other spores.

When there is a high concentration of mycotoxins, this brings about mold poisoning. They affect the respiratory system and the symptoms are similar to flu or cold. Some of the common poisoning symptoms include the following:

  • Itchy skin
  • Wheezing
  • Coughing
  • Nose stuffiness
  • Itchy/red eyes

Are you wondering the cause of black stuff in toilet? If you are trying to clean your toilet and still find black spots in toilet bowl, it would be better if you know the causes so that you can take the right measures.

There are so many things that can cause the development of black mold. The following are the most common causes of black mold


The toilet is one of the wettest areas in the house and this gives room for the development of black mold. There are several water fixtures that catch black mold which causes mildew. You need to wash it off at least twice a week with recommended chemical cleaners to prevent the development of mold.

“Broken floor tile”

This is another reason that stimulates the development of black mold in your toilet. If there are broken floor tiles in your bathroom, this can give room for water to stick under. This creates a warm and darker environment for mold to grow. Cleaning these cracks can be a tough job. The best thing you can do is to replace the tiles to prevent mold from developing in your bathroom.

“Toilet Leaks”

If there are leaks in your toilet that drip water for more than 48 hours, there are higher chances of black mold developing. You need to check for any leaks in your toilet and deal with it as soon as possible.

“Leaving your home for a long time”

If you leave your home for a long time, this means that you will not be flushing your toilet and black molds can develop. If you want to leave your toilet unflushed, then you can use chlorine to prevent mold from forming. When going for a vacation, put bleach on the toilet bowl as well as the water tank to prevent the formation of mold.

“Possible Places To Find Mold In A Toilet”

There are different places in your toilet where you can find black mold. I will take you several areas that you need to check for the presence of black mold. They include the following:

“Toilet bowl”

You can find black mold in your toilet bowl below the waterline and it is caused by several factors. One of the major causes of toilet mold is not flushing the toilet. If there is a lot of urine and solid deposits, there is a high chance of finding mold in the toilet bowl because they settle and start breeding.

Another cause could be the presence of black mold in the water supply. This causes mold to re-establish itself when you flush the toilet. Rust on the pipes can also cause condensation which leads to black mold. You can also check to find out if there are cracks on the ceramic of your toilet. The presence of cracks gives room for mold development.

“Toilet bowl”

You can also find black stuff under the toilet rim. Toilet rims are mainly open and let up. This means that it is easy for black mold to develop when the back mold spore get into contact with oxygen. If you also have hard water running in your bathroom, you can also experience black mold

“Toilet tank”

Toilet tanks are also breeding areas of black mold. This happens because they are mainly closed in a dark and warm environment. If it is rarely used, mold in toilet tank can get worse because chlorination that kills the mold will go down if it is not flushed.

Mold in toilet can also grow behind the toilet tank. If the tank is too close to the wall, then there are high chances of development of black mold. Another way in which molds develop behind the toilet bowl is when water drips between the toilet bowl and the wall. Not only do molds from behind the tank but also it can spread on other parts of the wall.

“How to Kill Mold in Your Toilet”

Now that you have found that there is black mold in your toilet, the next step is to look for ways to kill the mold. It can be stressful work but when you do it the right way, you will not experience any problems. The following are some of the ways to kill mold.

“Using vodka”

Vodka works well when it comes to killing mold. Spray vodka on the mold and then let it sit there for about 15 minutes. Then wipe it off using a sponge.


Vinegar works effectively in killing up to 82percent of mold and mildew. Spray it and then leave it for a while. It can give your bathroom a bad smell for some time but it eliminates mold.

If you want to kill mold that is developing inside the tank or under the lid, you can use chlorine bleach solution. You need to wear gloves when you are dealing with chlorine and you should also avoid inhaling the fumes. Once you shut off the toilet supply and flushing, fill the toilet tank with about hallway bleach solution, scrub the sides of the tank underside the lid and above the waterline. Once you rinse the sides with clear water, turn the water on and then flush the toilet several times to eliminate the residual bleach.

If there is mold outside the tank, you can clean it with the same solution. Wash the parts between the tank and the all with a long-handled scrubber. Chlorine has a bad smell so you can find it hard to use the bathroom until you rinse it several times with clean water.

If you do not want to deal with black mold, the best thing you can do is to prevent it from happening in the first place. Prevention is always better than cure. There are some preventive measures that you can take to ensure that black mold doesn’t develop in your toilet. They include the following:

  • Make sure you fix leaks as soon as they happen
  • Buy a humidifier to maintain the levels of moisture in your home
  • Ensure there is proper ventilation
  • Have an air purifier
  • Wash bathroom rugs often
  • Buy mildew resistant shower curtains
  • Avoid keeping shampoo bottles and shower gels in the toilet because they give room for mold to develop
  • Avoid carpets in bathrooms


If you find green or black stuff in your told or your tub, these are signs of the presence of black mold. This is a condition that you cannot ignore because it causes health problems for you and your children. You might end up experiencing pneumonia, asthma and other respiratory infections.

Black mold also causes mold poisoning which brings about a headache, rashes, fatigue, allergies, and other conditions. It is important if you know how to get rid of black mold as well as how to prevent it from developing. I have given you all the tips on how to prevent and get rid of black mold in your toilet. I believe you found this article resourceful and you will no longer have to deal with black mold again.

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