A refreshing suburban backyard swimming pool, perfect for summer days.

The Ultimate Guide to Pool Stains: Causes, Prevention, and Removal

A sparkling clean pool is the ultimate goal for every pool owner. However, over time, various types of stains can begin to appear, detracting from the beauty of your pool. Pool stains, whether they’re on the walls, floor, or waterline, can be a sign of imbalances in your pool chemistry or exposure to certain environmental factors.

Understanding the different types of pool stains, how to prevent them, and how to remove them is essential to keeping your pool in optimal condition. In this guide, we will explore the causes of pool stains, how to prevent them from occurring, and the most effective removal techniques to restore your pool to its pristine state.

Common Causes of Pool Stains

Before you can tackle pool stains, it’s essential to understand the causes. Pool stains can develop for a variety of reasons, from chemical imbalances to organic contamination. Identifying the underlying cause of the stain is key to choosing the best treatment method.

1. Metal Stains (Iron, Copper, and Manganese)

Metal stains are often caused by the presence of metals such as iron, copper, or manganese in your pool water. These metals can come from source water, metal pool equipment, or algaecides. Metal stains typically appear as rusty, green, or black marks on your pool surfaces.

  • Iron: Often causes brown or rust-colored stains.

  • Copper: Leads to blue or greenish stains, usually from copper-based algaecides.

  • Manganese: Causes black or dark purple stains.

2. Organic Stains (Algae, Leaves, and Debris)

Organic stains are caused by algae, leaves, debris, and other organic materials. These stains are commonly seen as green or brownish discolorations on the pool walls, floors, or waterline. Organic stains often appear after a heavy rain or windstorm when debris accumulates in the pool.

  • Algae: Typically causes green or black stains, especially in pools with poor filtration or unbalanced sanitizer levels.

  • Leaves/Debris: Can cause brown or green stains if not removed promptly.

3. Calcium or Chalk Stains

Hard water or high calcium levels can cause white, chalky deposits to form on your pool surfaces. These deposits, known as calcium scaling, are often seen around the waterline and on pool tiles. Calcium buildup can also create cloudy water if left untreated.

  • How to Spot It: These stains usually appear as flaky, white deposits that can be difficult to remove.

4. Sunblock, Lotions, and Oils

Sunblock, lotions, and oils brought into the pool by swimmers can cause oily stains on the pool’s surface. These stains are typically greasy and can create dark or cloudy patches on the pool floor or walls, especially in areas where swimmers frequently gather.

How to Prevent Pool Stains

Preventing pool stains is much easier than removing them once they’ve formed. With the right approach, you can minimize the chances of stains developing in your pool.

1. Regularly Test and Balance Your Pool Water

Regular testing and balancing of your pool’s water chemistry is one of the best ways to prevent stains. Ensuring that your pool’s pH, alkalinity, calcium hardness, and chlorine levels are within the ideal ranges will help prevent scaling and discoloration.

  • Ideal pH Level: 7.4 to 7.6

  • Ideal Alkalinity Level: 80 to 120 ppm

  • Ideal Calcium Hardness: 150 to 250 ppm

  • Ideal Chlorine Level: 3 to 5 ppm for chlorine pools

Testing and adjusting your pool water every week is key to preventing pool stains and keeping your water clear.

2. Use a Pool Cover

Covering your pool when it’s not in use helps keep debris, leaves, and contaminants out of the water, preventing organic stains. Pool covers can also help maintain your pool’s chemical balance by limiting evaporation, which can dilute sanitizer levels.

3. Maintain Proper Filtration

Regularly clean and replace your pool filter to ensure it is working effectively. A dirty or clogged filter can prevent the proper circulation of pool chemicals, leading to stagnant water and increased risk of staining.

  • Tip: Clean your pool filter every 1-2 months, or more frequently if needed, to maintain proper water circulation.

4. Control Metal Levels in Your Pool

If you live in an area with hard water or if your pool is exposed to metals, consider using a metal sequestrant. This chemical helps bind metals like copper and iron in the water, preventing them from reacting with chlorine and causing stains.

  • Tip: Regularly monitor the metal levels in your pool and add a sequestrant if necessary.

5. Encourage Swimmers to Shower Before Swimming

Swimmers bring oils, lotions, and dirt into the water, which can lead to staining over time. Encourage everyone to shower before entering the pool to reduce the amount of contaminants in the water.

6. Regularly Clean the Pool

Regular pool cleaning is essential to prevent organic debris from accumulating and causing stains. Vacuum the pool regularly, clean the walls and floor, and skim the surface to remove leaves and other debris.

How to Remove Different Types of Pool Stains

While prevention is key, stains can still happen. Fortunately, each type of stain has a specific treatment method that can effectively remove it.

1. Removing Metal Stains

Metal stains caused by iron, copper, or manganese can be tricky to remove. Here’s how to deal with them:

Use a Metal Stain Remover

  • What You Need: A pool metal stain remover (liquid or powder form).

  • How to Use:

    1. Test the water for metal levels.

    2. If levels are high, apply the metal stain remover to the affected areas.

    3. Run the pool filter to circulate the remover and allow it to neutralize the metals.

    4. Vacuum up any residue once the stain is gone.

Try Ascorbic Acid (Vitamin C)

  • What You Need: Vitamin C tablets or powder.

  • How to Use:

    1. Place the ascorbic acid directly on the stained area.

    2. Let it sit for a few minutes to dissolve the stain.

    3. Scrub the area gently to remove the stain.

  • Tip: Always test any product on a small, inconspicuous area first.

2. Removing Organic Stains

Organic stains caused by algae or debris can usually be removed with a combination of shocking the pool and using an algaecide or clarifier.

Shocking the Pool

  • What You Need: Pool shock (chlorine-based or non-chlorine shock).

  • How to Use:

    1. Shock your pool by adding the recommended dose of pool shock.

    2. Allow the water to circulate and run the filter for 24 hours.

    3. Brush the pool’s walls and floor to loosen any remaining stains.

Using an Algaecide or Clarifier

  • What You Need: Algaecide or clarifier.

  • How to Use:

    1. If algae are present, add the recommended amount of algaecide to the pool.

    2. Follow up with a clarifier to help break down and remove any organic material.

3. Removing Calcium Stains

Calcium buildup causes white, chalky deposits that are often found around the pool’s waterline.

Use a Calcium Hardness Reducer

  • What You Need: Calcium hardness reducer (liquid form).

  • How to Use:

    1. Add the recommended amount of calcium hardness reducer to the pool.

    2. Run the filter to circulate the chemical.

    3. Vacuum any remaining deposits from the pool.

Acid Wash (for Severe Cases)

  • What You Need: Muriatic acid (diluted with water).

  • How to Use:

    1. Dilute the muriatic acid and apply it to the stained areas.

    2. Scrub the stains with a soft brush.

    3. Rinse the pool thoroughly after cleaning.

  • Tip: Acid washing should be done cautiously and sparingly to avoid damaging the pool surface.

4. Removing Oil and Sunblock Stains

For oil and sunblock stains, using a surface cleaner or degreaser is often the most effective solution.

Use a Pool Surface Cleaner

  • What You Need: Pool surface cleaner or degreaser.

  • How to Use:

    1. Apply the surface cleaner to the stained area.

    2. Allow it to sit for a few minutes.

    3. Scrub the stain gently and rinse with clean water.

Try Baking Soda Paste

  • What You Need: Baking soda and water.

  • How to Use:

    1. Mix baking soda with water to form a paste.

    2. Apply the paste to the stain and scrub gently with a pool brush.

    3. Rinse the area with clean water.

Back to blog

Leave a comment