How Do I Get Brown Stains Off the Bottom of My Pool: A Complete Guide

Brown stains at the bottom of your swimming pool can be a frustrating eyesore. They not only look unappealing but may also indicate issues with water chemistry or filtration systems. Whether you own a concrete, vinyl, or fiberglass pool, dealing with brown stains promptly is essential for maintaining both the aesthetics and functionality of your swimming environment.

In this comprehensive guide, we’ll walk you through the most effective methods to remove brown pool stains. We’ll explain the common causes, the tools you need, and step-by-step strategies tailored to your pool type. Whether the stains are caused by metals, mold, or organic matter, this article will equip you with the knowledge and techniques to keep your pool clean and sparkling.

Table of Contents

Understanding the Cause of Brown Pool Stains

Before jumping into cleaning methods, it’s crucial to understand what causes those stubborn brown stains. Identifying the root cause can help you choose the most effective treatment and prevent future discoloration.

Common Causes of Brown Stains in Pools

Metal oxides – Iron, manganese, and copper can oxidize when the pH or chlorine levels are imbalanced, leaving behind brown or reddish stains.
Organic debris – Leaves, dirt, and algae can settle at the bottom and cause staining, especially in poorly circulated areas.
Mold or mildew – These can appear as brown or black spots, particularly in humid or shaded areas of the pool.
Poor water circulation – When water doesn’t circulate properly, contaminants can settle and stain the pool surface.
Improper chemical use – Using the wrong kind or dosage of chemicals can lead to staining, especially when they react with minerals in the water.

How to Determine the Type of Stain

A simple test can help you figure out whether you’re dealing with organic or metallic stains:

Drop a small amount of ascorbic acid (vitamin C) on the stain.
If the stain lightens or disappears, it’s likely caused by metals.
If it doesn’t react, it might be an organic stain caused by algae or debris.

Once you’ve identified the type, you can apply the best cleaning solution for your specific situation.

Tools and Supplies Needed for Pool Stain Removal

To effectively remove brown stains from your pool, you’ll need to invest in some essential tools and chemicals. Make sure you’re equipped before you begin the cleaning process.

Basic Cleaning Tools

Pool brush – Choose a brush that’s compatible with your pool surface (nylon for vinyl, stainless steel for concrete).
Pool vacuum – Ensure you have a manual or automatic vacuum suitable for your pool size and shape.
Skimmer net – Useful for removing floating debris before cleaning.
Test kit or strips – To monitor pH, chlorine, alkalinity, and metal levels.

Chemicals for Stain Removal

Chemical	Main Use
Metal sequestrant	Prevents and treats metal-based stains
Ascorbic acid	Effective for iron or manganese stains
Algaecide	Controls and prevents algae growth
pH increaser/decreaser	Maintains proper alkalinity and acidity
Chlorine granules or tablets	Kills bacteria and organic contaminants

Safety Equipment

Goggles
Chemical-resistant gloves
Face mask (optional, when handling strong chemicals)

Step-by-Step Methods to Remove Brown Pool Stains

Here’s a detailed breakdown of the most effective treatments, tailored to the causes of your brown stains.

Treating Metallic Stains

If your brown stains are caused by metals like iron, manganese, or copper, follow these steps:

Step 1: Test the Water

Use a reliable test kit to check for metal concentrations. High levels of metals will likely require sequestrants or chelating agents.

Step 2: Lower the Pool’s pH Temporarily

Metal stains tend to come off more easily in slightly acidic conditions. Lower the pH to around 6.8–7.0 for a short period before treatment.

Step 3: Apply Ascorbic Acid

Sprinkle crushed vitamin C tablets or ascorbic acid directly onto the stain. Scrub with a pool brush and let sit for 15–30 minutes before vacuuming.

Step 4: Vacuum and Filter

Vacuum the loosened debris and ensure the pool filter is running to remove any residual metal particles.

Step 5: Add a Metal Sequestrant

To prevent future staining, add a metal sequestrant or chelating agent to the water. This will keep metals in a soluble form and stop them from oxidizing and staining the pool surface.

Treating Organic Stains

If your stain is due to organic matter like leaves, dirt, or algae, follow these procedures:

Step 1: Brush the Area

Use a stiff brush appropriate for your pool type (nylon or stainless steel) to scrub the stain thoroughly. This helps loosen debris and disrupt the surface.

Step 2: Shock the Pool

Apply a strong dose of chlorine shock (either calcium hypochlorite or sodium dichlor) to kill algae and bacteria. Always follow manufacturer instructions for dosage.

Step 3: Run the Pool Filter Continuously

To remove dead algae and debris, run the filter for at least 8–12 hours or until the water clears.

Step 4: Add Algaecide

After shocking, add a broad-spectrum algaecide to prevent regrowth, especially if green or black algae contributed to the staining.

Step 5: Clean and Vacuum

Use the pool vacuum to remove all loosened particles, ensuring they do not settle and cause new stains.

Preventing Mold and Mildew

In areas with high humidity or limited sunlight, mold and mildew can lead to brown spots. Here’s how to address it:

Step 1: Scrub the Stained Area

Use a brush and cleaner designed for pool surfaces to scrub mold or mildew spots vigorously.

Step 2: Use a Disinfectant or Vinegar Solution

Mix equal parts of vinegar and water, apply it to the stained area, and let it sit for 30 minutes before scrubbing again.

Step 3: Increase Circulation

Ensure that the circulation is adequate by running the pump for longer periods and placing a portable pool water mover if necessary.

Step 4: Add a Clarifier

A clarifier helps bind microscopic particles, making them easier for the filter to catch and keeping your water clear.

Preventative Measures to Avoid Future Stains

Prevention is better than cure. By maintaining the right balance in your pool, you can significantly reduce your chances of dealing with brown stains again.

Maintain Proper Water Chemistry

Regular testing and balancing of water chemistry is key. Keep track of pH, alkalinity, chlorine levels, and calcium hardness. Ideally, your pool water should stay in these ranges:

pH: 7.2–7.8
Total Alkalinity: 80–120 ppm
Free Chlorine: 1–3 ppm
Calcium Hardness: 200–400 ppm

Use a Metal Sequestrant Year-Round

Even if you don’t notice metal stains now, using a sequestrant can help prevent them by keeping any dissolved metals in solution and invisible.

Brush Your Pool Regularly

Weekly brushing helps loosen dirt and algae before they have a chance to cause staining. It also promotes better circulation near the pool floor.

Vacuum Frequently

A clean pool means less debris settling and less chance of staining. Whether it’s a manual or automatic vacuum, regular use is essential.

Empty Your Skimmer and Pump Basket

Clogged baskets can reduce circulation and filtration efficiency. Clean them regularly to maintain water clarity and stain-free conditions.

Keep the Pool Covered When Not in Use

A pool cover helps prevent leaves, dirt, and even rainwater from entering the pool and causing staining. It’s especially useful for pools in shady or windy areas.

Tackling Stubborn Brown Stains: Advanced Techniques

Sometimes, even after conventional cleaning, the stains persist. In such cases, you may need to try more aggressive methods.

Giving the Pool a Stain Soak

For persistent stains, especially on concrete or plaster pools:

Step 1: Add Ascorbic Acid or Stain Remover

Gently pour or sprinkle the product directly on the stain.

Step 2: Cover the Stain

Use a piece of plastic sheeting or a pool stain sponge to cover the area and weigh it down with a pool noodle or tile.

Step 3: Let It Soak Overnight

Leave the treatment overnight to allow the chemical to penetrate the stain.

Step 4: Brush and Vacuum

In the morning, remove the plastic and brush the area thoroughly, then vacuum the remains.

Using Natural Remedies

If you prefer a less chemical-intensive approach, consider the following natural alternatives:

Baking soda: Can help scrub soft stains (but not effective against metal stains).
White vinegar: Useful for mildew or calcium buildup.
Pool enzymes: Break down organic contaminants naturally without harsh effects.

When to Call a Professional

If you’ve tried multiple methods and are still struggling with stains, consider hiring a professional pool service. They can perform a deep clean, test for hidden imbalances, and offer tailored solutions based on your pool’s construction and usage.

Pool Type-Specific Stain Removal Tips

Different pool surfaces respond differently to treatments. Here’s what to consider depending on your pool type:

Concrete/Plaster Pools

Concrete and plaster surfaces are porous and susceptible to deep-set stains. While effective, aggressive scrubbing can damage the finish. Use stainless steel brushes only and avoid abrasive chemicals unless specifically formulated for plaster.

Vinyl Liner Pools

Vinyl is more flexible and less prone to metal staining but can develop brown spots from organic matter. Use only soft brushes and non-abrasive cleaners to avoid tearing the liner.

Fiberglass Pools

Fiberglass is smooth and less likely to stain. However, once stained, it can be hard to remove without damaging the gel coat surface. Use gentle abrasives and avoid steel brushes.

Tile-Faced Pools

Tile surfaces are mostly used on pool walls, but if your floor has tile, be careful around grout lines—stains can set there easily. Use a smaller brush or even a toothbrush to clean grout deeply.

Maintaining Long-Term Pool Hygiene and Clarity

Stain removal is one part of pool maintenance, but consistent care is the best way to avoid future problems.

Regular Water Testing

Use a digital or liquid test kit at least once a week. Test more frequently after heavy use or after heavy rain.

Keeping a Maintenance Calendar

Track when you last cleaned, shocked, added sequestrant, or performed other key tasks. Use pool maintenance apps or calendars to stay organized.

Seasonal Maintenance Practices

In spring, perform a thorough cleaning and check all equipment.
After autumn, remove leaves and debris before they break down and stain.
In winter, cover the pool and maintain chemical levels for pools that stay active or semi-covered.

Educating Family Members

Teach anyone who uses the pool to shower before swimming and avoid bringing in garden debris or pool toys covered in dirt or sand.

Conclusion: Keep Your Pool Looking its Best

Brown stains at the bottom of your pool may seem stubborn and frustrating, but they’re entirely manageable with the right approach. From identifying the type of stain to using the proper chemicals and preventive techniques, maintaining a clean, clear pool is achievable for every pool owner.

By practicing regular maintenance, testing your water, and responding quickly to discoloration, you can ensure your swimming pool remains an inviting, stain-free space for years to come. Whether you choose DIY methods or consult a professional, staying proactive is the secret to success.

Now that you know how to get brown stains off the bottom of your pool, you’re well on your way to a pristine, enjoyable swimming environment. So roll up your sleeves, grab your brush, and dive into pool clarity!

What causes brown stains on the bottom of my pool?

Brown stains on the bottom of your pool are typically caused by the presence of metals in the water, especially iron, manganese, or copper. These metals can enter your pool through source water, such as well water, or from corroded pool equipment, pipes, or nearby soil erosion. When these metals oxidize due to chlorine or high pH levels, they form metal oxides that settle on the pool surface, leaving brownish or rust-colored stains.

While metal stains are common, it’s also possible that brown stains are the result of organic matter such as dirt, leaves, or algae buildup, especially in neglected pools or those with poor circulation. Identifying the exact cause of the stain is essential to choosing the right treatment method. A simple test using a vitamin C tablet or ascorbic acid on a small stain can help determine if it’s metal-related—stains that lighten or disappear are typically metal stains.

Can brushing alone remove brown stains from my pool floor?

Brushing is a vital step in pool maintenance and can help dislodge loose debris and light stains, but it’s typically not enough to fully remove brown stains, especially if they are caused by metals. Manual brushing with a stainless steel brush (for vinyl or fiberglass pools) or a nylon brush (for concrete pools) can break up the surface of the stain and help treatment chemicals penetrate more effectively. However, brushing without the proper stain-removing chemicals will not fully address the root cause of the stain.

In cases where staining is more severe or deeply set, brushing should only be considered a preparatory step. To completely eliminate brown stains, especially those caused by metal oxides, it’s important to use metal-specific stain removers, sequestering agents, or acidic treatments. Regular brushing combined with the proper water balance and chemical treatment can help prevent future staining and keep your pool floor clean and visually appealing.

How do I use ascorbic acid to remove brown pool stains?

Ascorbic acid is a common and effective treatment for removing metal-based stains from pools. To use it, start by turning off the pool pump to allow the water to settle. Then, sprinkle or gently pour ascorbic acid directly onto the brown stains. Wait for 10–15 minutes to allow the acid to break down the oxidation causing the discoloration. After this period, gently brush the area to lift the stain and then resume filter operation to circulate and clean the water.

It’s important to wear protective gloves and goggles when handling ascorbic acid and avoid inhaling its dust. The product works best on fresh or light stains, so heavily stained areas may require multiple applications. Additionally, after treatment, your water chemistry may change, so it’s essential to retest and rebalance your pool water to prevent further staining and maintain safe swimming conditions.

What are sequestering agents and how do they help prevent brown stains?

Sequestering agents are chemical compounds designed to bind with metals in your pool water, such as iron, copper, and manganese, preventing them from oxidizing and forming stains. These agents are often included in metal control products and are added regularly to pool water as part of a preventive maintenance program. They work by keeping metal ions in solution, so they do not settle onto the pool floor or walls and react with oxidizing agents like chlorine.

Including a sequestering agent in your regular pool care routine is especially important if you use well water or have a history of metal staining. These products provide long-term protection and are most effective when used before metal stains appear. While they won’t remove existing brown stains on their own, they play a crucial role in preventing new ones from forming after the stains have been treated with stain removers or ascorbic acid.

How does adjusting water chemistry prevent future brown stains?

Maintaining proper water chemistry is crucial in preventing brown stains from developing in your pool. Balanced water helps control metal solubility and oxidation, reducing the likelihood of staining. Key factors include maintaining a pH level between 7.2 and 7.8, avoiding high chlorine levels that can oxidize metals, and monitoring alkalinity and calcium hardness. If the water becomes too alkaline or too chlorinated, it can cause dissolved metals to oxidize and fall out of solution, leading to discoloration on the pool floor.

To address imbalances, use pH decreasers (like muriatic acid or sodium bisulfate) or increasers as needed. Regular water testing using a reliable test kit or strips will help you track these levels and adjust accordingly. Proper chemistry not only prevents stains but also extends the lifespan of your pool equipment and enhances swimmer comfort, making it an essential part of maintaining a clean and functional pool environment.

When should I call a professional to address persistent brown stains?

If you’ve tried multiple stain removal methods without success—such as using ascorbic acid, stain removers, and sequestering agents—or if the staining seems to be spreading aggressively, it may be time to call a professional pool service. Persistent stains can be a sign of deeper issues such as corrosion in your pool’s plumbing, a high concentration of unknown metals in your water source, or surface damage to the pool finish. A trained technician can conduct a more detailed analysis and apply industrial-grade treatments that may not be available to the average pool owner.

Additionally, if your pool surface is delicate or made of a material like plaster, vinyl, or fiberglass, incorrect use of acidic or harsh chemicals could cause damage. A professional will know the right products and techniques to safely restore your pool without harming the surface. Investing in expert help early can save time, money, and potential water quality issues in the long run.

Are there long-term maintenance tips to keep my pool floor free of stains?

To maintain a clean pool floor and prevent the recurrence of brown stains, routine maintenance is essential. This includes regular testing and balancing of pool water, using a skimmer and pool brush to remove debris, ensuring proper circulation with a functioning pump, and vacuuming frequently. It is also wise to install a water softener or use metal-removal filters for water sources known to contain high levels of metals, and to consistently use a sequestering agent in your chemical regimen.

In addition, monitor pool chemical levels carefully and avoid using algaecides or chlorine products that may contain high metal content. Draining and refilling your pool periodically—especially in areas prone to metal-rich water—can help reduce the buildup of minerals over time. Staying proactive with maintenance and promptly addressing any discoloration will keep your pool looking clean and prevent small stain issues from becoming major repairs or surface replacements.