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Toilet Bowl Yellow Stains | What Causes This?

Toilet bowl stains have the ability to make the entire bathroom look dirty. They are unsightly and can be a source of embarrassment if guests have to use the toilet. 

There are various reasons why yellow stains might appear in your toilet, and knowing the cause of the discoloration will help you to prevent a recurrence. In this article, I explain the causes of yellow toilet bowl stains and how you can get rid of them. 

Yellow toilet bowl stains are caused by limescale buildup in areas with hard water. It can also be the result of overusing bleach. Leaving urine to sit in the toilet bowl for long periods of time can lead to the development of stains.

Hard Water Creates Yellow Toilet Bowl Stains

Hard water is a major cause of toilet bowl stains. About 85% of US households have hard water, so there is a high possibility that the yellow stains in your toilet bowl are caused by hard water.


What Is Hard Water?

With the exception of distilled water, all water contains minerals and chemicals. Whether water is ‌hard or soft depends on the concentration of certain chemicals in the water.

Hard water is characterized by high concentrations of minerals like calcium, magnesium, and iron. 

Water mostly becomes hard when groundwater flows through limestone or chalk from where it absorbs mineral deposits. 

There are two types of hard water: temporary and permanent hard water.

Temporary hard water loses its hardness if it is boiled, while permanent hard water cannot lose its hardness simply by boiling the water. 

Hard water can lead to mineral buildup that has adverse effects on household fixtures, appliances, and plumbing connections. Hard water can also leave stains on glass, dishes, tubs, toilets, and even clothes.  

Here are ways to find out if you have hard water in your home: 

  • Add a few drops of liquid soap to a transparent bottle half filled with water, cover it and then shake the bottle vigorously. If there are no fluffy bubbles in the water and the water appears cloudy or milky, your water is probably hard. 
  • Request for a recent water testing report from your water provider.  
  • Use a water hardness test kit (amazon link). They can also be purchased at home improvement stores. 

Health Metric Pro Water Hardness Test Kit | Quick & Easy Hard Water Test Strips for Water Softener Dishwasher Well Spa and Pool Water | 50 Tester Strips at 0-425 ppm | Calcium & Magnesium Hardness

Why It Causes Yellow Staining

When you have water sitting on a surface, it has the potential to evaporate. When hard water evaporates, the mineral deposits are left behind because they are solids. These, particularly calcium, a.k.a., limescale, leave stains behind.

Toilet bowls are prone to hard water stains because they are constantly exposed to water. The presence of standing hard water in the toilet bowl means that there would always be mineral deposits in the toilet bowl.

Also, whenever you flush, lime scale can be released as water flows down the sides of the toilet bowl, which is why you also see stains higher up, where the water is not usually sitting.  

Now, limescale is just a solid that sticks to the toilet bowl, so it can be removed. However, the ease with which you can do this depends on how long the mineral deposits have been there.

Whenever limescale is left unattended for a prolonged period, it leads to mineral buildup, which leaves chalky-white/yellow or rust-colored stains on the toilet bowl

These stains are easy to differentiate from regular stains caused by poor toilet maintenance because they have a thicker composition and are more difficult to get rid of.

Hard water stains might not go away even after you’ve completed your regular cleaning. 

The stains can also be enhanced by a reaction between the minerals in the water and alkaline-based toilet cleaners. 

Besides discoloring the toilet bowl, hard water can also lead to clogs in your toilet drain. 

Bleach Can Discolor Porcelain

Bleach is a strong chemical. So, if used inappropriately, it can cause damage to porcelain, a delicate ceramic. 

Note: chlorine bleach is a whitening agent, so it should only be used to clean white toilet bowls. Using it on colored or pigmented toilets would lead to discoloration.

Bleach is highly corrosive and should be used with caution even while cleaning white toilet bowls. If the chemical is used carelessly, it can damage the porcelain surface and cause it to stain more easily

Careless usage of bleach includes applying undiluted bleach on porcelain, using too much bleach, or leaving it to sit on the surface for too long. 

Bleaching your toilet frequently can cause corrosion over time

Bleaching your toilet frequently can cause corrosion over time and if this happens, you will be left with stubborn yellow stains in your toilet bowl. 

Bleach should also not be used on vintage toilets. Using bleach to clean vintage toilet bowls can leave brown and yellow stains on their porcelain surface or it can completely disfigure the toilet bowl because these are far less protected than modern toilet bowls.  

The effect of bleach is worse in toilet bowls that are made of porcelain enamel because, in addition to its corrosive properties, the chemicals in bleach react with the iron in enamel, forcing it to oxidize. The oxidization process leaves rust stains on toilet bowls. 

Urine Will Stain Toilets if Left to Sit in the Bowl

Urine stains are caused by poor maintenance and are pretty easy to prevent. While most people think that it is the most common cause of stains, that’s simply not true. After all, toilet seats and toilet bases can also yellow.

There has to be a prolonged period of exposure for the stains to cling to the bowl, and this kind of exposure is not generally seen in homes.

But urine is capable of staining toilets. This is because urine contains a chemical called urochrome or urobilin. This chemical is responsible for the yellow pigmentation in urine.

Whenever urine is left to sit in the toilet, the bowl absorbs some of the pigments, resulting in a yellow stain.

The compounds in urine can also react with water temperature, PH levels, and the levels of limescale in water to form a urine scale. Urine scales are considered quite strong and leave yellow-brown stains in the toilet. 

Toilet wit traces of limescale, salt and stone deposit

Certain factors can increase the intensity of the stain.

For instance, damage to the porcelain surface would encourage urine stains to form. 

Also, urine oxidizes when exposed to air. So, the longer urine is left to sit in the toilet, the more intense the stain will be. 

Urine stains can be prevented by cleaning the toilet regularly and flushing immediately after using it. Thicker stains are more difficult to clean, so always clean the toilet bowl as soon as you notice discoloration. 

Besides the stain, if urine is left in the toilet for a prolonged period, it would lead to the buildup of ammonia, which is responsible for the offensive smell that’s associated with urinals. 

Can the Stains Be Removed?

Removing discolorations from a toilet bowl isn’t an impossible task. 

How difficult it is to remove a stain depends on the cause of the stain and how long it has stayed on the surface. For instance, urine stains are easier to clean than those caused by hard water and bleach

How to Remove Stains

While cleaning your toilet, do not use harsh chemicals or abrasive materials because they can scratch or cause damage to its porcelain surface. 

Here are ways you can clean toilet stains using household products. For best results, remove as much water as you can from the toilet bowl before you start, and repeat the required steps until the stains completely disappear. 

Method 1 of cleaning yellow stain on toilet bowl using baking soda and white vinegar

Method 1 (best for all types of toilet bowl stains)

  • Pour baking soda or borax on stained parts of the toilet bowl. 
  • Spread the powder around.
  • Add 1 and 1/2 cup of white vinegar to the bowl. 
  • Leave it on for 15-30 minutes and rinse. 
Method 2 of cleaning yellow stain on toilet bowl using lemon juice and essential oil

Method 2

  • Add 1 cup of lemon juice and 10-15 drops of essential oil to a spray bottle. 
  • Spray the solution on the toilet bowl, focusing on the stained areas. 
  • Leave it on for about 15 minutes and then rinse.
Method 3 of cleaning yellow stain on toilet bowl using baking soda and coke

Method 3

  • Add 2 tablespoons of baking soda to the toilet. 
  • Next, pour coke generously into the bowl. 
  • Leave it on for about 15 minutes.
  • Scrub and rinse the bowl.
Method 4 of cleaning yellow stain on toilet bowl using coke

Method 4

  • Pour coke generously on the toilet bowl. 
  • Leave it on for as long as possible. You can even leave it overnight. 
  • Rinse the bowl afterward.

NB: If you are battling stains caused by hard water, the best way to address the issue for good is to install a water softener. 


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