Decode the Culprits: What Causes Brown Stains in Swimming Pool?

Marjan Sokolovski

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Causes Brown Stains in Swimming Pools

A crystal-clear swimming pool is an inviting oasis, but the unsightly presence of brown stains can mar its allure. These mysterious brown blemishes on your pool’s surface can leave you wondering about their origins. 

In our blog post on ‘what causes brown stains in swimming pools’ we dive deep into this common pool issue, shedding light on the various factors that contribute to these unattractive marks. 

From metals like iron and copper to organic matter such as leaves and debris, tannins from plant matter, and even water chemistry imbalances, we explore the diverse sources of these stains. 

The root causes are the first step towards effectively preventing and removing brown stains, ensuring that your pool remains a pristine oasis for relaxation and enjoyment. So, stay sharp. 

What Causes Brown Stains in Swimming Pools?

Brown stains in pools can result from various sources, including metals like iron and copper leaching into the water and oxidizing. 

Also, organic matter such as leaves and debris decomposing, tannins from plant matter like leaves, rust from metal components, and imbalanced water chemistry with high pH or alkalinity levels cause metals to precipitate out. 

These stains can mar the pool’s appearance. Proper maintenance, regular cleaning, and use of sequestrants can help prevent and treat brown staining. 

Identifying the specific cause of staining is essential for effective removal, and consulting professionals may be necessary for persistent or severe stains. 

Ongoing vigilance and water chemistry management are key to keeping your pool clear and inviting.

What Are the Brown Stains on the Bottom of the Pool?

Brown stains on the bottom of a pool can have various causes, and identifying the source of these stains is crucial for effective removal and prevention. 

Some common reasons for brown stains on the pool bottom include:


Iron and copper are often responsible for brown stains on the pool floor. 

These metals can enter the pool water from various sources, including rusty pool equipment, well water, or nearby landscaping with iron or copper content. 

When oxidized, they can precipitate out of the water and create brown stains on the pool surface.

Organic Matter

Organic debris, such as fallen leaves, twigs, and dirt, can accumulate on the pool bottom. 

Over time, these materials decompose, leaving behind brown stains. Algae growth can also lead to brownish-green stains if not properly treated.


Tannins are natural compounds found in plants, particularly in leaves and wood. If leaves or other plant matter enter the pool, tannins can leach into the water and cause brown staining on the pool floor.

Water Chemistry Imbalance

An imbalance in the pool’s water chemistry, including high pH or alkalinity levels, can lead to the precipitation of metals and the formation of brown stains on the pool bottom.

If the staining is severe or persists despite your efforts, it may be necessary to consult a professional pool service to identify the specific cause and implement an appropriate solution.

How to Get Rid of Brown Spots in Pool Bottom?

Get Rid of Brown Spots in Pool Bottom

Getting rid of those pesky brown spots in the pool bottom doesn’t have to be a head-scratcher, folks. So grab your pool brush and let’s get down and dirty.

Detect the Culprit

First things first, you gotta play detective. Find out what’s causing these brown spots bottom of the pool.

Whether it is metals, organic junk, tannins, or some other pool party crasher. Knowing your enemy helps you pick the right weapon to fight it off.

Brush and Vacuum

Roll up your sleeves and grab that pool brush. Scrub away at those spots to loosen ’em up. 

Then, suck ’em out with a pool vacuum like you’re on a mission. This one-two punch can already make a world of difference.

Shock It, Baby

If those spots are thanks to organic crud or algae, time to shock the pool with a good ol’ chlorine treatment. 

Follow the instructions on the shock treatment label to know just how much oomph to use based on your pool size.

Stain Remover Squad

For the tough cookies, a stain remover product designed to tackle metal and organic stains is your secret weapon. Read the label and use it like a pro.

Metal Sequestrant Back-Up 

If the spots are caused by metal mischief, deploy a metal sequestrant. Add the right amount according to the label, and keep it in line to prevent more staining.

Balance the Chemistry

Don’t forget to keep your pool’s water chemistry in check. If your pool’s pH and alkalinity are out of whack, it’s an open invitation for more stains. Adjust the chemistry to keep ’em at bay.

Don’t Give Up

Stubborn stains may need multiple rounds in the ring. Be patient and don’t back down!

Fortify Your Defenses

To stop those brown spots from staging a comeback, stay on top of water chemistry, use a sequestrant when needed, and keep your pool spick and span.

If the going gets tough and you’re stumped, call in the big guns – a professional pool service.

They can perform water testing, identify the specific cause of staining, and recommend appropriate treatments.

How to Clean Brown Spots on Pool Floor?

Clean Brown Spots on Pool Floor

Cleaning brown spots on a pool floor can be a bit challenging, but it’s essential to maintain a clean and inviting pool. 

Here are some key steps to help you effectively clean brown spots on the pool floor:

Detect the Cause 

Determine the source of the brown spots. Are they caused by metals, organic matter, tannins, or something else? Understanding the cause will guide your cleaning approach.

Proper Brush and Vacuum

Start by brushing the stained areas with a pool brush. This helps to loosen the spots and prepare them for removal. 

Follow up by using a pool vacuum to remove the dislodged particles and debris. This initial step can significantly improve the appearance of the spots.

Use a Stain Remover

If the brown spots bottom of the pool are stubborn and difficult to remove, consider using a pool stain remover specifically designed to target metal and organic stains. 

Follow the product’s instructions carefully, as application methods and contact times may vary.

Shock Treatment

If the brown spots are the result of organic matter or algae, shock your pool with a chlorine-based shock treatment. 

Follow the manufacturer’s guidelines for the correct dosage based on your pool size. This helps to eliminate the source of staining.

Prevent Future Staining

To avoid the return of brown spots, maintain proper water chemistry, use a metal sequestrant if necessary to prevent metal staining, and keep your pool free of debris. 

Regular pool maintenance and vigilance in water chemistry management are key to preventing future brown spots.

If you’re uncertain about the cause of the brown spots or have difficulty removing them, consider consulting a professional pool service. 

They can conduct water testing, identify the specific cause of staining, and recommend suitable treatments.

Tips to Keep Stay Away From Brown Spots on the Bottom of Pool

Brown Stains on the Bottom of the Pool

Preventing brown spots on the bottom of your pool is key to maintaining its appearance and water quality. 

Here are some tips to help you avoid brown spots:

Regular Cleaning and Maintenance

  • Consistent pool maintenance is crucial. Regularly skim the surface, vacuum the pool, and clean the pool’s walls to remove debris and prevent the accumulation of organic matter.
  • Use a pool brush to scrub the pool surfaces, which can help prevent the buildup of organic matter and algae that may lead to brown staining.

Balanced Water Chemistry

  • Maintain proper water chemistry by regularly testing and adjusting the pH, alkalinity, and chlorine levels in your pool. Imbalanced water can cause metals to precipitate and form stains.
  • Use a quality pool water testing kit to monitor and manage the water’s chemical balance, ensuring it remains within recommended ranges.

Metal Sequestrant

Consider using a metal sequestrant if your pool water has a high metal content. This product can help prevent metals like iron and copper from staining the pool surfaces by binding to them and keeping them in suspension.

Landscaping and Tree Maintenance

  • Be mindful of the landscaping around your pool. If you have trees nearby, regularly trim branches and remove leaves to reduce the likelihood of tannins and organic matter entering the pool water.
  • Ensure that any metal fixtures, such as handrails or pool furniture, are in good condition and not prone to rusting.

Regular Shock Treatments

  • Shock your pool regularly with a chlorine-based shock treatment to maintain proper sanitization and prevent the growth of algae and other organic matter.
  • Routine shock treatments can help keep your pool water clear and free from potential sources of brown staining.

By following these tips and maintaining a proactive approach to pool care, you can minimize the risk of brown spots on the bottom of your pool and enjoy a clean and inviting swimming environment throughout the season.


What causes brown stains on the bottom of the pool?

Brown stains on the bottom of a pool are often caused by organic materials like leaves, algae, or iron deposits from source water. They can also result from insufficient water chemistry maintenance, leading to metal oxidation.

What causes stains on pool walls?

Brown stains on pool walls typically occur due to metal or mineral content in the pool water, such as iron or copper. These metals can react with the pool’s surfaces, causing discoloration.

What chemical removes brown pool stains?

The chemical commonly used to remove brown pool stains is a sequestrant or metal stain remover. These chemicals bind to metals and minerals in the water, preventing them from staining the pool surfaces.

Are the brown stains on the pool floor washable?

Brown stains on a pool floor are not usually washable. Cleaning them typically involves using appropriate chemicals and scrubbing or brushing the affected areas.

Why is my pool plaster turning brown?

Pool plaster can turn brown due to several factors, including improper water chemistry, algae growth, or metal content in the pool water. 

Maintaining proper water balance and addressing any metal issues can help prevent and mitigate plaster discoloration.

Wrapping Up

The battle against brown stains in your swimming pool can be won through knowledge and proactive maintenance. 

By identifying the root causes, you can implement the right strategies to prevent and address these blemishes effectively. 

Regular cleaning, balanced water chemistry, and the use of metal sequestrants when needed are essential steps in maintaining a sparkling pool. 

Moreover, ensuring your pool is free from organic debris, tannins, and metal-prone sources like rusting fixtures can go a long way in preventing staining. 

With these insights and preventative measures, you can enjoy a pristine pool, free from the frustrations of unsightly brown stains, creating the perfect environment for relaxation and recreation. Best wishes. 

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Marjan Sokolovski

I am a professional swimming coach who has been coaching for over 20 years. I have coached athletes in the Olympics and Paralympics, and I have also helped to train people across the world. I started my coaching career by teaching swimming lessons at a local pool. I was really passionate about teaching people how to swim, but I quickly realized that this wasn't enough for me. I wanted to make a difference in people's lives and help them achieve their goals. I started working with athletes in high school, college, and then professionally. The best part about coaching is that you get the opportunity to work with so many different types of people from all walks of life - it's just incredible! LinkedIn

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