Mold in Toilet Tank: Causes, Prevention and Removal

Graphic toilet including a toilet tank

Bathrooms or toilets have more humidity than any other part of your home. The reason is the presence of water and low ventilation.

Have you ever been to a toilet with an open water container showing mold inside it? Unattended toilets often have mold in them, and it’s not something difficult to deal with. Despite being an extremely unwelcoming sight, mold in a toilet tank is very common and easy to remove as well.

If it’s this issue is has been bothering you for a while and you are unsure about what it is, how it happens, and ways to get rid of it, then you have come to the right place.

Today, we will share the importance of cleaning a toilet tank, how to remove mold in 15 minutes, and what health problems a mold toilet can cause.

What is mold and what causes mold in a toilet tank?

Like any other place with mold, toilet mold is also the result of a humid, dark, and warm environment. Mold in your toilet tank does not differ from fungus in any other part of your home. There is not a specific type of mold that develops in toilet tanks, but the good news is that this fungus is easy to prevent or remove from breeding in your toilet.

Mold also appears in many colors, but the tank mold tends to be black, and it forms a ring in your toilet. However, the ring color can be black or green, and grey mold is common too. If the mold is slimy, then the color is most likely to be pinkish or orange. Typically, mold in the toilet tank develops when the water sits inside the tank and toilet bowl.

Causes of mold in bathroom tank


The most common cause of mold is humidity. Bathrooms and toilets have more humidity, which makes them the perfect breeding place for mold. The tank hosts water all the time, making it the most humid spot. It’s easy for airborne mold to take place inside the bowl when it’s left open.

Stagnant water

In case a toilet is used frequently and the tank water changes regularly, it’s least likely to grow mold in it compared to toilets used infrequently. One of the major causes of decay in the tank is stagnant water. That’s why the toilet should be flushed whenever it’s used so that the container fills up with fresh water. When your tank hosts mold, the spores are passed to the toilet bowl. However, the toilet bowl can have fungus even if the toilet tank is clean. Here is a good solution for cleaning the bowl.

Infrequent use

If the mold is only present in the water tank and not in the toilet bowl, the most probable cause is infrequent use. It gets quite warm in a toilet tank, making the perfect breeding conditions for mold to grow. Besides, when the toilet is not used enough, chlorine added to the water to prevent mold growth will sit down in the tank — helping mold to grow effortlessly.

Worn-out washer

A major contributor to the growth of mold is a worn-out washer. If you see mold underneath the tank, it means the washer is damaged. A worn-out washer causes the water to drip out slowly, inviting airborne mold to grow underneath the tank. The best way to deal with this problem is to remove the mold and then replace the washer.

How do I get rid of the mold?

Since mold is hazardous, you must be wearing a protective mask to protect your eyes and prevent mold spores’ inhalation. Also, wear gloves before inserting your hand into the toilet tank.

To remove the toilet mold and prevent further growth of mold in the container, you need to do the following procedures.

A fun fact is that survival training experts advise considering toilet tank water as an emergency drinking water supply (it’s technically potable since it comes from the water supply). This is a good incentive to avoid harsh chemicals as well as protecting the surface of your toilet tank. The following procedures should safely clean the mold with readily available household products:

  1. The best thing you can use for the initial treatment is the mixture of distilled vinegar and water. Pour the mixture into the tank and leave it for 2 hours.
  2. Flush the toilet multiple times.
  3. In case there is still mold in the container, turn off the valve, empty the container, and use a toilet brush to thoroughly clean the toilet tank. Scrub the parts having toilet mold.
  4. Now turn on the water valve, let the toilet fill with water, and flush the tank multiple times.
  5. After the initial cleaning, now add another cup of vinegar and leave it for one hour.
  6. After one hour, flush the toilet multiple times and remove mold.


To ensure that mold doesn’t come back, you should clean the water tank regularly. Whenever you use the toilet, flush the tank. The more you use the toilet and flush it, the fewer chances there’ll be of mold in the tank.

Can mold in the toilet in a bathroom make you sick?

Mold breeding in your toilet tank releases pores, and you may inhale them because of their airborne nature. It’s relatively harmless, but mold can trigger reactions to those allergic to it, given the right circumstances. People with underlying health conditions like asthma can experience discomfort from it.

Also, if mold appears within a few days after removing it from the tank, it indicates that your house hosts mold in the entire home.

Soo…that black stuff in my toilet tank also mold?

Have you ever lifted the lid of your toilet tank and found black staining inside the container and wondering what it is? It’s a common problem found in many households and the public use toilets. The black stuff in the toilet tank can be mold, particles of worn-out washers, or manganese.

Dark mold can adopt your toilet container in its breeding place if the water tank has stagnant water or is used infrequently. But there’s nothing to be extra concerned about it. Dealing with black mold in the toilet container the same way you deal with other types of mold can get you rid of it.

How do you clean the inside of a toilet tank?

If your toilet tank or bowl has mold in it, then you certainly need to clean it. However, keeping it clean for the entire time will help maintain its condition.

First, you need to empty the water tank. Turn off its water valve to prevent refilling. Now take off the lid and empty the water tank completely. Depending on fast the water flows, you may need to perform multiple flushes.

Now that you have an empty tank, you’ll be able to get a comprehensive idea of the tank’s condition. If you’re only looking to at the surface grime, then it can be cleaned with scrubbing. However, if there’s any sort of buildup, use vinegar and baking soda.

Wear a rubber glove and spray the tank and its parts with a cleaner of your choice. Now use a scrub brush to clean all the parts and remove any buildup from them. After cleaning the tank, fill it with water and flush multiple times.

We hope this guide helps you learn about the causes of mold in the toilet tank and its prevention and removal methods.

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