What Causes Black Mold In Toilet Bowl? Troubleshooting Guide

Helen Skeates
Helen Skeates
22 min read

Assume it’s not an alien invasion the next time you see black mold growing in your toilet bowl or toilet tank. Despite the fact that black mold thrives in moist, dark environments like a toilet tank, it is quite simple to remove. You probably already have the cleaning supplies you need to get rid of the mold.

What Causes Black Mold?

When it comes to mold, there are several reasons why your toilet could become an ideal breeding environment. To put it another way, mold is a type of fungus that thrives in damp environments, according to the CDC. In the event that your toilet has not been used for a few days or if a small amount of waste remains in the bowl, Shield Home Watch Services warns that black mold can grow. In addition, because mold thrives in dark and moist conditions, you may see black mold growing in your toilet bowl and tank.

What Causes Black Ring In Toilet Bowl - Your Toilet Doctor

If you have black mold in your toilet, which is ugly and no one wants, you may easily remove it without using harsh chemicals. You don’t want black mold to stay in your toilet for too long, even though it’s easy to remove. Even if you are in perfect health, exposure to mold can be hazardous to your health. Mold can cause a runny nose, wheezing, red or itchy eyes and skin, hay fever, and shortness of breath, according to the Centers for Disease Control and Prevention (CDC).

Natural Cleaning Solution

To begin the process of removing black mold from your toilet tank or bowl, you’ll need to gather the necessary cleaning supplies. To avoid catching mold spores in your eyes, the EPA suggests using a N95 face mask, long gloves, and goggles. In the opinion of Shield Home Watch Services, white vinegar is the greatest natural way to get rid of the black mold in your toilet. You can use a spray bottle to apply the vinegar.

The first step is to spritz the vinegar into the bowl and let it sit for a few seconds before using. Use a toilet bowl scrubber to remove the black ring after letting the vinegar soak. Keep repeating these procedures until the black ring disappears. Repeatedly flush the toilet after the black ring has disappeared ensures that the vinegar is gone.

Following the bowl, you must also clean the tank. The tank may be cleaned by adding a cup of bleach and letting it sit for 20 to 30 minutes at a time. Scrub the tank walls, but be careful not to touch the tank’s internal components. Flushing the toilet and discarding the gloves and brush will ensure that no mold spores remain once the black mold has been removed.

How to Stop Mold Growth

Shield Home Watch Services says that the best approach to avoid black mold is to prevent it from growing in the first place. As a preventative measure, the experts advise that you get some preventive medications. Every time you flush, a preventative tablet releases a small amount of its ingredients into the tank. This will help to maintain your toilet free of filth and mold growth in the long run!

Getting Rid Of Black Toilet Mold

To begin with, you must take safety precautions before coming into touch with molds of any kind. Make sure you’re well-protected by donning gloves, a mask, and cleaning supplies. Baking soda, vinegar, borax, and a cup of bleach can all be used for the latter.

The window should be left open to allow the air to circulate freely and prevent mold spores from entering the room. Additionally, flushing the toilet to reveal any impacted areas is an important step in the pre-cleaning process.

Drain cleaner can be added at this point. Then, apply some baking soda or borax on the bowl specifically on the waterline. Brush the area gently with an old toothbrush or a hard brush after spraying vinegar on it.

It’s time to put the answer away for a few minutes. It’s time for a last scrubbing and rinsing before adding some bleach to the water and drying it off. Wait an hour after adding the bleach to the toilet water.

Flushing the toilet with hot, bubbly water before using bleach will improve its efficacy. The operation can be repeated as many times as necessary until you are satisfied with the outcome.

Preventing Black Toilet Mold

The easiest way to avoid wasting time, effort and resources is to discover how to prevent the regrowth of toilet mold (especially the black ones). Always keep an eye on what’s going down the toilet. Using a scrub brush and a cleaning chemical like Concrobium Mold Control, make it a habit to clean your toilet at least once or twice a week.

You should flush your toilet every other day if you don’t use it very often to prevent molds from taking advantage of it. Fix any bathroom leaks as soon as possible since mold can grow in wet conditions.

Where Does the Toilet Mold Form?

Minerals, fungi, and filth on the porcelain surface of your bowl can lead to the formation of toilet mold, but spores can also be found in other areas. You’ll find it in the shower, the kitchen sink, caulk, and many other locations.

In addition to deteriorating the toilet’s performance, mold can also destroy the toilet’s white finish. Black mold, on the other hand, may develop virtually anywhere:

Option 1: Mold in the Toilet Bowl

Your toilet bowl is a breeding ground for black mold because of the constant presence of water. There are mineral deposits in Stillwater that contribute to the accumulation of trash.

The black ring around the water’s surface is visible most of the time. Mold growth is aided by keeping water in contact with the air. The black mold, on the other hand, is prone to growing both in and beneath water, as well as under the lip of the toilet bowl.

Your toilet’s lifespan may be shortened if you use this foul-smelling material.

Option 2: Mold in the Toilet Tank

It’s possible to find black mold in your toilet tank. As time passes, the walls and bottom of your tank accumulate trash and minerals. Grime also builds up around the toilet flapper to damage it.

It’s also fair to state that most people don’t bother to open and clean their toilet tank. Because you’re only doing it when there’s a major issue, it’s only reasonable that you’d find mold inside.

Option 3: Mold Around the Base of Your Toilet Bowl

It’s also possible for mold to form at the bottom of your toilet bowl, where water sits all the time. Your bathroom toilet may be leaking, and you should look for cracks in your throne to find the source of the leak.

Option 4: It Hides Behind the Tank

There is no mold underneath your toilet tank, thus this is the most difficult option. If you don’t see black mold on the opposite side of the tank, that doesn’t mean it’s not developing.

In order to notice mold stains, you must stand directly against the tank’s wall. Because mold tends to grow to the tank’s edges, it should be easy to spot the indicators of debris.

What Causes Black Mold in Your Toilet?

When water sits in your toilet bowl, biological detritus accumulates into the black mold you see there. Here’s what causes your toilet to fill up with a dark stuff.

Hard Water

The ring in your toilet is caused by water with a high mineral content. These deposits can’t be digested by your toilet, so they end up floating to the top of the water.

Stagnant Water

If you have hard and stagnant water, the toilet will surely suffer from mold and dark stains. Stillwater collects particles, deposits, and waste. All these elements pollute water and make the toilet look dirty.

You Don’t Use Your Toilet Often

Having hard and stagnant water can cause mold and brown stains in the toilet. Pollution and garbage can be found in Stillwater. Wastewater from these sources is polluted by all of them and appears unclean in the toilet.

Occasionally, you may detect mold growing beneath the toilet seat as well.

Moisture and Darkness

Mold thrives in moist, dark places. As a result of its moisture and obscurity, your bathroom is an ideal breeding ground for the black mold, which thrives there.

Rusty Pipes

It is common for many toilets to have rusty metal parts and hoses. Corrosion contaminates water and discolors the toilet’s glazed porcelain surface. Also, the tank, its background, and even the base are affected by this effect.

Cracks in the Toilet

The tank bolts or other plumbing components in an old toilet may be leaking, making it vulnerable to cracks and other issues. Once more, it offers an ideal environment for the growth of mold.

Cracked bowls can’t be cleaned because the black mold keeps growing until the bowl is replaced.

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How to Clean Mold From the Toilet Bowl?

It’s a good idea to know how to get rid of toilet mold because you don’t want to keep it there for long. If you’re serious about getting it done, here are the actions you’ll need to take:

Step 1: Prepare Your Tools

Rubber gloves, a face mask, goggles, a scrub brush, a bucket, a sponge, vinegar, and baking soda are all necessary tools for toilet bowl cleaning. It’s important to remove all of the mold before beginning the process of cleaning it.

Step 2: Ventilate the Bathroom

Ventilate the bathroom while you’re cleaning the toilet to avoid a nasty stench. Open the doors and windows to allow fresh air to circulate. Exhaust fans can also be used to promote ventilation.

Step 3: Get the Water Out

Use a sponge and a small cup to remove the excess water from the dish. You can use a bucket to collect the waste water from flushing the toilet once. Drain cleaner can be poured down the drain when the bowl is empty to clean and shine the pipes.

Step 4: Clean It With Vinegar and Baking Soda

The next step is to use white vinegar and baking soda to remove the mold from the porcelain. Apply a tiny amount of each product to the spots and gently scrape them.

Strong mold marks can be removed with the toilet brush as well. After that, you should let the mixture sit for 20 minutes before washing it again with the toilet brush.

With a piece of cloth, wipe down the bowl of the toilet and you’ll be amazed at how clean it looks.

How to Remove Mold From the Toilet Tank?

The second lesson teaches you how to remove mold from the tank of a toilet. ” Once you’ve switched off the toilet’s water supply by twisting a knob behind the toilet, you’re ready to begin.

The tank lid can be removed by hand. After that, follow these mold removal steps:

Step 1: Pour Vinegar With a Spray Bottle

The tank lid can be removed by hand. After that, follow these mold removal steps:

Remove the tank lid by hand. Follow these steps for mold eradication after that:

Step 2: Scrub the Tank

After letting the vinegar work its magic for about 20 minutes, begin washing the tank’s walls with a rag or an old cloth. It’s best to proceed with caution to avoid damaging the tank or any of its components.

Step 3: Pour a Bucket of Water

Fill a bucket with hot water and get started. Don’t use hot water, since it can soften and ruin the plastic in the tank. Flush the toilet while it’s full to watch the stains go away.

Repeat the cleaning method if you can still notice mold in the tank after the initial cleaning.

Step 4: Open the Shutoff Valve

The tank top must be replaced and the shutdown valve must be opened after the mold has been removed. You can then reinstall the tank and use the toilet once more.

How to Remove Black Mold From the Back of the Tank?

You may also use this mold removal procedure to remove the black material from the back of your toilet.

Step 1: Remove the Tank

Close the water supply, flush the tank, then remove the fill pipe underneath it to remove it. You can remove the hose with pliers because it has a metal thread nut attached to the tank.

Find a few fasteners to keep the tank firmly on the metal foundation after that. Pliers can be used to loosen the tank by twisting them counterclockwise. Because the tank is now empty and light, you can lift it with your hands.

Step 2: Clean the Tank

Place the tank so that the backside faces upwards. To clean the tank’s back, use the same vinegar and baking soda solution, but let it sit for 20 minutes before scrubbing.

Cloth or a rag can then be used to remove the remaining mold stains from the surface. When you’re finished, use clean water to thoroughly rinse the surface. If the tank’s rear is still dirty and screwed up, repeat the operation.

Step 3: Reinstall the Tank

Reassembling the tank after the mold has been removed is the final and easiest procedure. Reinstall the tank, tighten the tank nuts, and connect the fill hose.

After that, turn on the main water valve and let the tank to fill up. Once the toilet tank is filled, you can flush it to see whether it works; there is no mold problem, therefore it should.

Is Black Mold in Your Toilet Dangerous?

Inhaling or ingesting toilet mold can be dangerous, but this seldom occurs. The first thing to keep in mind is that you don’t spend a lot of time in there. Most stains, on the other hand, are too small to cause harmful gas emissions.

However, persons with allergies, asthma, and other acute health disorders may be harmed by the black matter in your toilet. Itchy eyes, a stuffy nose, a scratchy throat, or even a rash are all possible side effects.

Even though these problems are quite rare, you don’t want to risk your health. In order to remove the mold from the tank after flushing, you need to know how.

How to Prevent Black Mold in the Toilet?

These anti-mold tips and hacks will help you avoid mold in the first place, so don’t forget about them.

Clean Regularly

To begin, make a habit of cleaning your toilets on a regular basis. To avoid the growth of toilet mold, don’t leave it in the bowl for too long. Keep it clean at all times by using antibacterial treatments and equipment.

Ensure Proper Ventilation

Mold prevention necessitates frequent bathroom ventilation. There is nothing more simple than opening the window and letting in some fresh air. Installing the best exhaust fan is another alternative for keeping out moisture and dampness.

Bathrooms are equipped with exhaust fans in order to combat the buildup of moisture.

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Use Dehumidifiers

A bathroom dehumidifier is another option. You can use the best dehumidifiers to remove dampness from your toilet. What is the mechanism by which they operate?

In the bathroom, you may adjust the humidity level so that you can control the amount of moisture in the air.

Flush the Toilet Frequently

In addition, you can flush your toilet frequently to remove any material that may have accumulated in the bowl, as well as human waste. It will keep the water moving and preventing it from accumulating and forming disgusting dark stuff.

Every day, flushing the toilet keeps black mold at bay and prevents it from forming in the tank.

Fix Possible Leaks

Finally, look for any fractures or leaks in the toilet’s seal. Do your utmost to fix the toilet or install a new one that functions properly if you discover any issues.

Does Mold in My Toilet Indicate Diabetes?

You don’t necessarily have diabetes if you see mold in your toilet because of moisture and dirt. As a result, their urine contains more sugar since their bodies are unable to metabolize it.

A mildew and mold have a field day in this environment.

Black mold thrives in the glucose-rich liquid. If you’re concerned about your health, it’s a good idea to check for diabetes. The mold is coming from somewhere else if you get a negative result.

Do You See Black Stuff in Toilet After Flushing?

After flushing, you may also detect a black substance in the bowl. If you find white mold, which is less prevalent than black mold, you’ll want to remove it as well.

Rusted plumbing pipes are frequently the source of the issue. After flushing, rust may create a dark substance. In addition, hard water may be delivering to your toilet supply system.

Adding a little soil to your toilet bowl might cause mineral deposits to transform into the black gunk in the bowl. There is, however, a silver lining: Black mold may be cleaned in the same way as white mold.

The Bottom Line

After flushing, no one likes to see black mold growing on the toilet bowl since it’s unsightly and perhaps hazardous. Debris and moisture are the primary reasons for the rapid growth of mold spores and mildew in bathrooms.

Black mold can be a real nightmare, but it can also be prevented from developing. The toilet is moisture-free thanks to regular cleaning solutions and dehumidifiers. If you use them as a preventative measure, your toilet will always be free of odors.


How do you get rid of the black mold in the toilet?

The only way to remove the black mold is to thoroughly clean the toilet, and this will depend on where it is located. To avoid further black mold growth, you can employ a variety of instruments and techniques.

What is the black sediment in my toilet bowl?

Mold is the source of the black scum in your toilet bowl. Mold grows when water remains for an extended period of time, allowing dirt, mineral deposits, and other particles to build and grow.


Not only do you want to keep your bathroom as spotless as possible, but you need also practice good hygiene in order to avoid developing black mold in your toilet bowl. It appears that ignoring mold growth is a bad idea.

Helen Skeates

Helen Skeates

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