How To Get Rid Of Black Residue In The Toilet?

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Last Updated on January 11, 2023 by acechapman

Mold or mildew is likely to cause dark spots, black residue, or rings in your toilet bowl. While the color may change to a different color over time, it is generally black.

Bad ventilation, dampness, and stagnant water are the main causes of black mold in bathrooms. Use vinegar to break down the mold and a brush to clean it up. Other commercial mold removers or steamers can be used to get rid of it.

Although mold is a very common problem in bathrooms, it can be unsightly and could cause a negative image of hygiene. Mold tends to cause damage to what it grows on. It can do more damage the longer it grows. Here’s a detailed discussion on the causes and how to prevent mold growth.

What is Black Residue or Mold in the Toilet?

Black residue or mold in a toilet can be caused by a variety of factors. One of the most common causes is a buildup of mineral deposits, such as calcium and magnesium, which can occur when hard water is used for flushing and cleaning the toilet. This type of buildup is usually found around the rim of the toilet bowl and can be difficult to remove.

A fungus known as black discoloration, which can sometimes be orange or green, grows vigorously in moist, dark, warm environments. Bathrooms are ideal habitats for fungus.

If you notice black residue or mold in your toilet, it is important to clean it thoroughly and regularly to prevent it from spreading.

black residue in toilet

What Causes Black Residue in The Toilet?

Toilet mold is not as common as other discolorations, such as brown stains in the toilets that can be associated with poor water quality. Instead, it is mostly caused by moisture. Here are the top causes of mold in bathrooms.

  • One of the main causes of mildew is the infrequent use of the toilet. This creates warm, moist conditions that are ideal for mold growth. Reduced flushing also reduces chlorination, which helps to destroy mold.
  • Stagnant Water – The tank is the most neglected part of the toilet. The mold thrives in stagnant water, so it is not cleaned up.
  • The mold thrives more in darkness if the tank is covered with a lid.
  • Mineral deposits – these are the surfaces like tank walls and hard water deposits that provide mold with a source of nutrients. Mold will infest the tank more often if there is more water left in it. The type of water can also affect the condition. Hard water has more minerals than soft.
  • If you find mold under the tank, this could indicate a worn washer. The washer’s purpose is to prevent water from entering the washer. If mold is found in the washer, this means that the washer is not performing its task properly.
  • Mold growth can be encouraged by human waste from the toilet. Mold loves sugar so more sugar can promote mold growth.
  • Black mold can also be caused by water supply pipes. Condensation can also be caused by rust on pipes, which can lead to mold growth. This is the main reason for recurring black residue, especially in your tank.
  • Mold can be caused by cracks in ceramic bowls, tanks, or other fixtures for bathrooms. These cracks give the fungus an environment conducive to growth and stickiness.

How to get rid of the black residue or mold in the toilet bowl?

Black stains can be found in the bowl under the rim, at the waterline, or at the base/bottom.

Mold at the waterline can indicate that you don’t use the toilet often. It could also mean that your tank has become infested and it is time to clean it up.

If mold develops below the water line or more around the base, it is possible that you have a damaged water seal and need immediate attention from a plumber. A broken seal indicates a leak beneath or at the water inlet.

Leakage means that there is moisture in the area, which can lead to mold growth. To stop the leak, you will need to replace the wax ring and clean the area.

Here are the steps for cleaning mold from a bowl. These items and cleaners are essential.

  • Protective Gear: gloves, goggles, and a respirator (preferably an N95 respirator to avoid inhaling the airborne mold).
  • Toilet brush, bucket, and rags
  • Cleaning products and solutions: Bleach, vinegar, bleaching, baking soda, borax, and steam cleaner.

Vinegar Method

  1. To ensure proper ventilation, open the doors and windows of your bathroom.
  2. Protect your hands with gloves, and cover your face with a mask and goggles.
  3. To see the mold spots around the water line and bottom, flush the toilet.
  4. Spray vinegar in the bowl to prevent mildew. Let it sit for between 15 and 30 minutes.
  5. Remove the mold by scraping it off.
  6. Rinse with water and remove any vinegar.
  7. Continue repeating steps 4, 5, and 6 until the mold is gone.
  8. Clean up and disinfect your cleaning products after use.

Vinegar & Baking Soda Method

  1. In a bowl, add 1 cup of vinegar.
  2. Spray baking soda in the bowl. Don’t forget to spray the area under the bowl rim.
  3. Cover the bowl with a lid and allow the vinegar/baking soda to sit in the toilet for approximately half an hour to an hour.
  4. To remove mold stains, gently scrub the bowl with a toothbrush, toilet brush, or other non-abrasive tools. Make sure the brush goes all the way around the bowl, including below the rim.
  5. Allow the toilet to sit for another 15 minutes.
  6. For a clean rinse, flush the toilet.
  7. Repeat the process if mold remains.

Steam Cleaner Method

This is an easy way to get rid of mold in your bathroom without using chemicals. This multipurpose steamer comes with 18 attachments and is affordable!

  1. Place the attachment for the angle nozzle on the hose.
  2. Steam the toilet bowl base, under the rim, and water line with high pressure while wearing protective gear to remove stains.
  3. To remove any mold or rust from screws, heat the bowl and the edges of the toilet seat.
  4. To wash the dirt from the toilet bowl, fill a spray bottle with vinegar.
  5. Finally, flush the toilet.

You can also use bleach to clean the toilet bowl. Mix one gallon of water with one cup of bleach and place it in the bowl for 15-30 minutes. Bleach disinfects the toilet bowl and gives it a thorough cleaning. It is important to remember that bleach alone does not kill all mold.

black residue in toilet

How To Deal With Black Residue Or Mold in the Toilet Tank

After you have found the mold in your water tank, it is important to thoroughly clean the tank to prevent it from spreading to the bowl or other parts of the toilet. You can clean it in a variety of ways, including simple DIY methods like vinegar or lemon juice mixed together with baking soda.

Materials Required:

  • Gentle hand brushing
  • Vinegar


  1. Add distilled vinegar to the tank
  2. Allow the vinegar solution to sit for 30 minutes.
  3. To remove any mold, flush the tank a few times.
  4. Continue this process until you are satisfied.

For a more intense cleaning, you can add baking to the tank. Important to remember that concentrated vinegar and bleach can cause damage to some components of the tank. Make sure to avoid bleaching and that the vinegar has been distilled.

How to get rid of mold behind a toilet tank?

Mold can also grow if water gets into the tank from the back. It is easy to remove mold from the tank. Here’s how:

Materials Required

  • Container or bucket
  • Rags
  • Gentle hand brushing
  • Vinegar
  • Baking soda
  • Disinfectant/ Bleach


  1. To see the source of mold, wipe down the tank’s back.
  2. Use baking soda and vinegar to make a paste. Make sure the paste is thick enough that it sticks to the tank.
  3. Spread the paste on the mold-infested areas, making sure to cover every inch of the back.
  4. Use the hand brush to gently scrub the grout lines of the tank.
  5. It can be left on for up to half an hour.
  6. To remove any mold, gently scrub the back of your toilet.
  7. Use a rag or sponge to clean any spots that need more scrubbing. Continue to scrub until you are satisfied with your results.
  8. For a clean finish, spray clean water over the area. To disinfect, you can also use bleach.
  9. Repeat until the mold spots and stains are gone.

Why is there black residue in the toilet after flushing?

If your toilet is stained with a black substance after you flush it, this could be a sign that your pipes are leaking or have rust. Leaks and rust can harbor black mold which is then transferred into your toilet tank. Also, high levels of iron in the water can cause staining and discoloration. If the iron is in its ferrous state, it can cause black residue and can be more likely to happen after flushing.

However, the presence of a black residue could be a sign that the water is not working correctly. It could be that the water is dirty or has mineral deposits.

How to Prevent Mold Growth in Bathrooms & Toilets

These simple preventive steps can be taken to stop mold growth.

  • After you have taken a shower, ventilate the bathroom. The area will stay cool and dry by opening the windows or using an AC conditioner. This prevents mold growth.
  • When you are unable to open your windows, such as at night and during cold seasons, use dehumidifiers.
  • After using the toilet, always clean it up. Even if you only use the toilet for a moment, flush your waste.
  • Use scrubbers and chlorinated cleaners to clean your toilets regularly.
  • As soon as possible, fix any bathroom leaks.
  • To prevent mold and mildew growth, put some borax in your toilet.
  • Remember to inspect the area(s) affected after cleaning to ensure there is no mold or water damage.
  • To prevent condensation, cover cold surfaces such as cold water pipes with insulation
  • Vent the bathroom with appliances that create moisture, like clothes dryers or heaters, to reduce humidity.
  • Ensure surfaces and bathroom appliances are dry before you paint or caulk them. Paint and caulk are not designed to kill mold, and paint that is applied over moldy surfaces will likely peel.

If none of those mentioned methods or prevention measures work, or the situation seems out of your control you might want to contact a specialist who is skilled in indoor mold removal.

Can Black Residue or Mold in the Toilet Bowl Cause Diabetes?

There is no direct link between black residue or mold in the toilet bowl and diabetes. Black residue or mold can be caused by a buildup of mineral deposits, poor ventilation, or poor maintenance, and is primarily a cosmetic and sanitation concern.

Diabetes is a chronic medical condition characterized by high levels of sugar (glucose) in the blood. It is caused by problems with the way the body produces or uses insulin, a hormone that regulates glucose levels. The main risk factors for diabetes include being overweight or obese, having a family history of the disease, and leading a sedentary lifestyle.

Although there is no direct link between black residue or mold in the toilet and diabetes, it is important to keep the bathroom and toilet clean and well-maintained to prevent the growth of mold and bacteria, and to promote overall health and hygiene.

Practice good hygiene and cleanliness, especially when it comes to areas that have contact with human waste like toilets. It’s important to keep them clean and well-maintained not only for aesthetic reasons but also for health purposes.

Can Toilet Mold Make You Sick?

Black mold can grow in the tank, behind the tank, and under the toilet bowl. This can pose a danger to anyone, whether they are healthy or not. EPA, and other experts in health, mold exposure can cause a stuffy nose and wheeze. Itchy eyes, skin reddening, hay fever, and shortness of breath.

This is especially true for people who are allergic. You should have safety precautions in place to prevent mold from growing. To prevent allergic reactions from occurring, you could wear a respirator while cleaning.

Wrapping Up

This is basically how to get rid of black residue or mold in the toilet bowl. This method does not remove the black stains, but it will prevent them from coming back. The black residue will remain in your fixtures and toilet bowl as long as your water supply is high in manganese.

Hard water mineral deposits can also cause premature failure of appliances such as dishwashers and washing machines. Although it is more cost-effective and will last for a longer time, a water softener may be a better solution.

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