Toilet Seat Turning Black – Causes and Fixes

A home’s toilet is a lot more significant than most people realize. To have a safe and healthy household, you must always keep it clean. Unfortunately, you might notice black stains on your toilet seat or under the toilet lid and wonder what on earth they could be.

Black stains, mold stains, or soot on a toilet seat can be attributed to various things. This situation is often caused by hard water, fumes coming from a gas burner, and damaged pipes.

Bad as this might seem, there are solutions. In this article, you’ll find more in-depth explanations of why toilet seats turn black and how to deal with it.

Black Residue Left on Toilet Seat

Seeing black stains on a toilet seat may worry you. Not only can this make you feel bad about your bathroom not being clean, but it may also signal something hazardous to you and your family’s health: soot, mold, and even buildup from gas burners.

Black soot can be harmful to both humans and pets. To deal with black soot residue on your toilet seat, it is imperative to know why it is happening.

Let’s have a close look at some of the possible culprits behind black soot on a toilet seat:

toilet seat

Hard Water

When a toilet seat appears to be turning black, it’s usually not actually changed color. Instead, it’s accumulating some type of residue on its surface. 

One of the biggest reasons for this residue is hard water. Hard water consists of water and elevated levels of dissolved minerals like calcium, iron, and magnesium. Over time, these minerals oxidize, harden, and form a black soot on surfaces wetted with hard water.

This chemical reaction between oxygen and minerals causes dark oxide compounds to get onto the toilet seat, making it look as if it is turning black.

Completely changing your water supply is next to impossible for most of us. However, you can learn how to remove these stains later in this article.


The closer your toilet seat is to a kitchen or fireplace, the more likely it is to accumulate soot from another source: gas burners. 

Since toilet seats are generally made from plastic, the fumes from a gas burner or fireplace can form dark stains on the surface of the plastic. These stains can be difficult to remove.

Bad Plumbing

No one expects a toilet seat to stay perfectly new forever, but black stains, mold, or soot indicate something is awry. Bad plumbing can be one cause.

Unfortunately, you have to employ professional help when it comes to bad plumbing. This can cost a lot of time and money. However, hiring professionals will ensure that the problem gets correctly solved and black soot no longer forms on the seat.

Lack of Maintenance

A clean, functioning toilet is essential to any home or business, and regular maintenance is required for this to be the case. Such care includes washing the toilet seat properly to remove and prevent black mold stains and soot from building up.

Failing to regularly clean a toilet seat can make you perceive that the seat itself is changing color. An unclean toilet seat is sure to have germs such as Streptococcus, Staphylococcus, and E. coli.

However, maintaining your toilet correctly will ensure that stains, mold, and bacteria don’t fester on the seat.

Solutions to Residue on Toilet Seat

When cleaning a toilet, you should check everywhere for signs that something is wrong—not just the seat. By doing so, you can discover signs of black residue that has spread and needs additional attention. You might find black soot, mold, or stains on or around the toilet seat, under the rim, or under the toilet tank.

Solutions to a toilet that seems to be turning black include using bleach or a steam cleaner, as described below:

Using Bleach to Clean Soot

Bleach is a cleaning agent that most people have in their homes, and it can help you get rid of the black soot on your toilet seat. The CDC (Centers for Disease Control and Prevention) suggests mixing 1 cup of bleach with a gallon of water for cleaning. Here are the steps to follow:

1. Always wear rubber gloves and goggles to protect your skin and eyes.

2. Mix the gallon of water and cup of bleach.

3. Scrub the black soot, mold, or stains off the toilet seat.

4. You might have to scrub for 15 minutes or so. Keep going until the soot is all gone.

Steam Cleaning Soot

Depending on how stubborn the soot on your toilet seat is, you might need to clean it off with a steam cleaner.

1. Adjust the pressure on the steam cleaner and steam the affected area of the toilet bowl. For your safety, do this as gently as possible.

2. Clean any black residue off with a household cleaner, such as the bleach and water solution above.

Why Is the Inside of My Toilet Tank Black?

Some people find black residue inside their toilet tank instead of their toilet seat. The inside of your toilet tank can accumulate black residue for the same reasons mentioned above: minerals, mold, and general debris.

The water in the toilet tank will appear dark black, but it will look like clean water when you flush it. This can make it hard to notice this situation since most people don’t look inside their toilet tank very often. You might incidentally find dark stains on the inside of the tank while investigating a different issue with your toilet.

To clean your toilet tank, empty the water and clean it thoroughly with a bleach cleaner and toilet brush or other scrubber. Ensure adequate ventilation for cleaning with such solutions.


Black soot, mold, or stains on a toilet seat does not mean that you have to throw it away and install a new one. Typically, a simple household cleaning solution or tool will be enough to eliminate the stains. If necessary, seek professional guidance.