What Causes Black Stains in Toilet Bowl?

It is usually pretty obvious what causes certain colors to appear in our toilets depending on what we have been doing in there most recently – yellow and brown usually make sense. But what about when you find a color like black? What causes black stains in toilet bowl?

close dirty flush toilet house

If you need to know what causes black stains in toilet bowl and how to get rid of them, read on for the answer.

What Creates Black Stains on Toilet Bowl?

A few things could be what causes black stains in the toilet bowl, with the main culprits being hard water, bacteria, and mildew.

  • Hard water. The mineral deposits left from hard water use can collect in places with a heavy flow, such as your toilet. The black, brown, red rust or grey waterlines in your toilet bowl are seen where the flow is the heaviest.
  • Bacteria. This usually has a pink color to it, but if bacteria build-up, it could appear black. The type of bacteria is normally found in toilet bowls is called Serratia marcescens, and it can transfer into your bowl via feces.
  • Mold and mildew. If your toilet is infrequently used and the water is left stagnant for long periods of time, your toilet may develop mold and/or mildew. These could be what causes black stains in toilet bowl because mildew need both an organic surface to grow on and a moist environment.

In particular, the hard water deposits in your toilet bowl, especially under the rim, can satisfy these conditions and therefore provide an ideal breeding ground for these types of organisms.

The hard water and bacteria may not be pretty, but they are at least relatively harmless. However, black mold can be dangerous to your health. As such, it is recommended to remove black mold from your toilet as soon as possible.

Read on to find out how to best remove these types of organisms.

What Tools Will You Need to Remove Black Stains from a Toilet?

cleaning supply bucket kitchen counter

To get rid of black stains from a toilet, you will need:

*While technically not necessary for the cleaning, some protective gear like this will help keep you safe from the mold, as it is a fungus that produces spores.

How Do You Remove of Black Stains from a Toilet?

You can choose only one of these methods or opt for both if you have especially stubborn black stains. The first step for all of them is the same; however: ventilate the room as best you can and put on your protective gear.

Method 1: Vinegar

Step 1: Flush the toilet and get rid of water

You want a clear view of the black spots and water lines.

Step 2: Sprinkle baking soda or Borax, then spray vinegar

Concentrate on getting the baking soda or Borax on the waterline and any black spots – do not forget to get underneath the rim! Spray vinegar on the baking soda. While you have the vinegar out, also put about a cup of it into the tank with the water. If there happens to be something also growing in your tank, this will help clean it too.

Step 3: Wait and then scrub

Let the bowl sit with the solution for about 1-1.5 hours. Scrub with your toilet brush, scrub brush or even Magic Eraser. You can also scrub the toilet tank if you like but be careful of everything in there! Some of the parts in there are delicate, so if you happen to hit or break something while in there, you may cause a whole new problem with your toilet.

Step 4: Wait some more, then flush

Let the freshly scrubbed bowl sit with the solution for at least 15 minutes. Flush.

Method 2: Bleach OR Hydrogen Peroxide

Step 1: Add bleach to bowl

Dump about 1 cup of bleach or hydrogen peroxide into your toilet bowl, making sure to pour it both in the toilet water and around the bowl (again, do not forget under the rim!). You can also add about a cup to the toilet tank as well at this time.

Step 2: Scrub

Scrub all around the bowl, but really concentrating on the stains with your scrubbing tool of choice. Again, you can also scrub the tank (but be careful!).

Step 3: Wait

Let it sit for at least 15 minutes to let the bleach or hydrogen peroxide do the work of killing any potential bacteria.

Step 4: Flush

Flush a couple of times until you have removed all the cleaning solution.

The Inside of Your Toilet Bowl is Stained Black.

What is Going On With Your Water?

door handle open to toilet can see toilet

There is probably nothing wrong with the water itself. The black stains could just be a result of hard water build-up, and that is natural and largely harmless.

But of course, there is a chance that there is something wrong with the water. If you think that this is the case, check with whoever oversees the water supply in your area to see if they have any answers. Perhaps they already know about the issue and can provide solutions.

Why Is There Black Stuff in Toilet After Flushing?

If you notice black stuff specifically after flushing and have ruled out any issues with the water itself, and do not think that it is just a result of hard water, it could be that mold is growing in and around your water supply pipes.

Your pipes may be rusty or leaky, creating an ideal breeding ground for mold. The mold could therefore be coming in with the water from the pipes that lead to your toilet.

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