Mold in Toilet Bowl Below Water Line: How to Get Rid of It

Mold in a toilet bowl can be embarrassing and very annoying, so knowing how to win the mold war within the toilet bowl can be quite an accomplishment. So how do we get rid of mold in a toilet bowl that is below the water line?

How to Get Rid of Mold Below the Water Line in a Toilet Bowl

Below we discover various ways of tackling the mold below the water line in the toilet bowl, as well as learn how to prevent it from coming back.

Cleaning a moldy toilet

Hydrogen Peroxide to Get Rid of Mold Below Water Line in Toilet Bowl

Hydrogen peroxide (3%) kills mold and mold spores by breaking down their DNA and proteins. Although hydrogen peroxide is effective at killing mold, it’s not recommended for non-porous surfaces.

Pour about a half cup of hydrogen peroxide into the toilet bowl along with one cup of baking soda and let sit for at least 15 minutes. Scrub the toilet bowl with a scrub brush and flush to rinse.

Repeat twice weekly to keep bacteria and mold away.

Bleach to Get Rid of Mold Below Water Line in Toilet Bowl

Although bleach can kill mold, it’s not recommended by the EPA. Pouring one-half cup of bleach into the toilet bowl and scrubbing with a scrub brush can be effective in killing mold, but make sure you do not put bleach into the toilet tank, as bleach can corrode the inner parts of a toilet.

Vinegar to Get Rid of Mold Below Water Line in Toilet Bowl

Vinegar is a highly recommended means of killing mold and should be used in the toilet bowl twice weekly along with a scrub brush. Keep large containers of vinegar in the bathroom for easy access, and add 1 cup of vinegar to the toilet tank three times per week.

How to Prevent Mold in the Toilet Bowl

Now that we know how to kill the mold in our toilet bowls, let’s go over some ways we can prevent mold from coming back.

Use Vinegar to Prevent Mold in the Toilet Bowl

Use vinegar twice weekly with a scrub brush to stop the recurrence of the mold. In order to prevent mold, you need to pour 1 cup of vinegar into the toilet tank three times every week.

Improve Ventilation to Prevent Mold in the Toilet Bowl

Improving the ventilation in a bathroom can prevent the accumulation of moisture in the air, otherwise known as humidity. It’s recommended to run the fan during every bath and shower, leaving it running for some time afterward. Opening a nearby window after bathing will also help contribute to good ventilation within a home.

The lack of ventilation in a bathroom makes for an environment practically begging for mold.

Flush Immediately to Prevent Mold in the Toilet Bowl

Flushing immediately to prevent mold in the toilet bowl is strongly recommended, as mold needs a food supply in order to thrive. Human waste that contains sugar makes mold especially happy, so be sure to flush after every toilet visit.

Does Mold Grow Underwater?

Mold is not able to grow underwater, as there is not enough oxygen for mold to survive. Mold can, however, survive if only partially submerged in water.

What Causes Black Mold in the Toilet Bowl?

Black mold in the toilet bowl is caused by infrequent toilet use, the dark and moist environment that mold thrives on, condensation on nearby pipes, stagnant water, human waste, mineral deposits, and cracked ceramic on the toilet bowl.

Let’s cover each of these individually to get a better idea of the causes of black mold in the toilet bowl.

Mineral Deposits Causing Toilet Mold

Mineral deposits contribute to mold by giving the mold a nutrient-rich feast to devour. Hard water is a term used for water in a home that contains more minerals than soft water. Homes with hard water are more apt to have more mineral deposits in toilet bowls and toilet tanks.

Human Waste Causing Toilet Mold

Human waste left unflushed in a toilet bowl provides nutrients for mold to survive on. Human waste containing any levels of sugar makes mold especially happy and want to set up a permanent camp right there in your toilet.

Needless to say, make sure that you flush immediately when done using the toilet.

Cracked Ceramic Causing Toilet Mold

Cracks in the ceramic toilet bowl or tank provide inviting nooks and crannies for mold to grow. These dark, tiny spaces hold moisture, making these prime breeding grounds for mold.

Darkness Causing Toilet Mold

The darkness of a toilet surrounded by water is a prime breeding ground for mold. Fungus thrives in this environment, so being on top of a cleaning routine is paramount.

Infrequent Toilet Use Causing Toilet Mold

Infrequent toilet use can cause mold, as stagnant water is the ideal environment for mold to grow. Toilets that are used less often are far more apt to experience an accumulation of mold and mildew due to their infrequent usage.

If you have a toilet in an area of the home that is not used as often, try flushing it periodically to keep the water circulating.

Condensation on Pipes Causing Toilet Mold

Condensation on pipes can be caused by air cooling on cold pipes and toilet tanks, producing condensation. This is more of an occurrence during the summertime when the humidity levels are higher, which in turn means a higher dew point.

Is Toilet Mold Dangerous?

Toilet mold is not dangerous to those in good health and may cause no reaction or only a mild allergic reaction such as sneezing when inhaling mold spores.

For those suffering from a more severe ailment such as asthma, bronchitis, or emphysema, exposure to pollution and other airborne irritants such as mold spores can cause a more serious reaction such as wheezing and difficulty breathing.

Is Black Mold in the Toilet Tank Dangerous?

Based on current research and according to Medical News Today, black mold is no more dangerous than any other type of mold. Yet mold in general can cause an allergic reaction in those sensitive to airborne pollutants.

Asthma sufferers may be particularly sensitive to the presence of mold, as mold spores become airborne and can cause mild to serious allergic reactions to the mold.

Let’s face it, mold in a toilet is embarrassing. Know, however, that just because the mold is black does not mean it’s any more harmful than any other type of mold. Mold is mold, despite its color.

How to Get Rid of Black Mold in a Toilet Tank

Get rid of black mold in a toilet tank by using a vinegar solution. Turn the water valve to the off position. The water valve is usually behind the toilet, near the floor. Flush the toilet until all of the water has completely emptied from the toilet tank.

Using either all vinegar or a vinegar and water solution of 50/50 parts, let sit for at least half of the day, making sure to use another toilet if needed.

Turn the water valve back on and flush out the vinegar water. Once the vinegar solution is flushed away completely, turn the water valve back off. Once again, flush until all of the water has drained from the toilet tank.

Using a toilet brush and a non-bleach disinfectant, scrub the inside of the toilet tank, wiping with paper towels. Turn the water valve back to the on position and flush a few times.

Vinegar is a natural mold killer and will combat almost all types of mold. Just make sure to never use bleach inside your toilet tank.

Can I Put Bleach in My Toilet Tank?

Putting bleach in a toilet tank can corrode the inner parts of the toilet such as the rubber seals and metal parts. Although bleach does not harm the porcelain itself, putting bleach in a toilet tank is strongly discouraged. Cleaning tablets that contain bleach should be avoided.

For unsightly mineral build-up and other questionable matter, pour four cups of vinegar into the toilet tank and allow it to soak for an extended period of time, at least an hour.

After the toilet tank has soaked in the vinegar solution, turn off the water valve that is typically found near the floor behind the toilet.

Flush the toilet until the water has drained the toilet tank. Now that the toilet tank is completely drained of water, spray a bleach-free disinfectant inside of the tank and let stand for about 15 minutes. Scrub the inside clean with a toilet brush and wipe with paper towels.

Another option is to fill the empty toilet tank with 50% vinegar and 50% water and let sit for up to twelve hours, making sure to use a different toilet during that time.

When done soaking and cleaning with a toilet brush, turn the water back on and flush a few times to rinse the toilet tank of any residual crud that was washed off.


Trina Greenfield, Author
SmackDown Media LLC

About the Author:
Trina Greenfield, the owner of SmackDown Media LLC, is passionate about providing information to those interested in the air quality in and around their homes. Trina writes content about things she’s passionate about, such as safe, in-home air, educational platforms for children and adults, as well as all things family-related.