Why Is My Pool Turning Green?

Swimming in a green pool is, at best, a mistake and, at worst, can cause serious health problems. But what causes this familiar, frustrating problem for pool owners? The main reasons tend to be algae growth, chemical imbalances, and poor filtration. In fact, 85% of pool owners experience algae growth at some point, which is the most common cause of green water in pools. Armed with this knowledge, we can get our pool back to how it’s supposed to be – clear and inviting.

With a proper maintenance regime, we can fix this common problem and prevent it from returning. By following the steps below, you can keep your pool healthy and fun all season.

Key Takeaways

• Algae growth is the number one cause of green pool water.
• Chemical imbalances will stop chlorine from working.
• Regular filtration maintenance is key to clear water.

Consider a Professional Pool Inspection

If your pool keeps turning green and you’re not sure why, it might be time for a professional pool inspection. An expert can catch hidden issues with your circulation system, filtration, or even small leaks that you might miss — saving you time, money, and a lot of green water headaches.

Algae Growth

In certain conditions, green algae can double in number every 24 hours, typically in warm weather and sunlight. Knowing the different types of algae that can flourish in pools and why they tend to grow can help us fix the problem.

Types of Algae That Cause Green Pools

Several types of algae can make our pool water look green, including:

Green Algae: This is the most common. It forms a thin layer on the water’s surface or can be seen floating. It loves warm, sunlit water.

Mustard Algae: This type looks like yellowish dust. It sticks to walls and steps and is hard to remove. Mustard algae grow in areas with poor circulation.

Black Algae: This is the hardest to kill and manifests as small dark spots on the water’s surface. Frustratingly, it also has a protective layer, so it’s resistant to chlorine. Proper treatment is needed to get rid of it.

What Encourages Algae to Grow?

There are several reasons for algae to grow in our pools, including:

• Sunlight: Direct sunlight feeds algae photosynthesis. Pools with lots of sunlight will grow faster.
• Temperature: Warmer water temperature makes it easier for algae to grow. Most algae grow above 70°F.
• pH Imbalance: If our pool’s pH is not balanced (ideally between 7.2 and 7.8) chlorine will not work. This creates an environment for algae to grow.
• Nutrient Availability: Algae feeds on nutrients found in organic matter and debris. High levels of these nutrients (often from leaves or grass) can cause rapid growth.
• Circulation: A pool will turn green if the water is not circulating enough, so run the pool pump 10-12 hours in summer and 6-8 hours in winter to keep water moving when the sun is out.
• Dirty Filter: A dirty filter hinders circulation and won’t be able to filter the water anymore, so check the filter pressure regularly and clean or backwash it as needed to keep it working properly.

Chemical Imbalances

Proper chemical levels in our pool are key to a clean and safe swimming environment. We need to consider pH, chlorine, and alkalinity as these are the factors that prevent algae growth and clear water.

Why We Need to Maintain Proper Chemical Levels (pH, Chlorine, Alkalinity)

To keep our pool water balanced, we need to test and adjust three main elements: pH, chlorine, and alkalinity.

• pH: The ideal pH range is 7.2 to 7.8. Levels outside this range will reduce chlorine’s effectiveness and let unwanted organisms grow.
• Chlorine: Our first line of defense against bacteria and algae. We should aim for 1-3 ppm (parts per million) for optimal disinfection.
• Alkalinity: To stabilize pH, total alkalinity should be between 80-120 ppm.
• CYA Level: Keep CYA between 30-100 ppm (30 for chlorine pools, 60 for salt) to prevent sunlight from burning off chlorine too quickly. A high CYA (over 100) causes “chlorine lock,” so using liquid chlorine in winter helps maintain balance.
• Phosphate: Phosphate is fertilizer for algae, so keeping levels below 200 ppm and using a phosphate remover as needed deprives algae of essential nutrients and keeps your pool clear.

How Chemical Imbalances Create an Environment for Algae Growth

When our pool’s chemical levels are off, we create a home for algae. Two factors contribute to this:

1. Low chlorine: When chlorine is not enough, algae will grow unchecked. Chlorine needs to be in the recommended range to kill these organisms.
2. High pH: When the pH is too high, chlorine will not work. Algae can grow even if we use chlorine, and we’ll end up with a green pool.

Inadequate Filtration

Inadequate filtration can make our pool green by not removing debris and preventing algae growth. 40% of pool owners with green pools report having filtration problems. Understanding how the filtration system works and spotting signs of poor performance is key. Since the average lifespan of a pool filter is 5-7 years, we need to monitor its condition to keep our pool clean.

Why a Proper Filtration System is Important for Pool Maintenance

• Captures Debris: The filtration system removes dirt, leaves, and debris from the pool water and prevents pollution.
• Prevents Algae Growth: Without proper filtration, organic matter can accumulate and create an environment in which algae can grow.
• Maintains Water Circulation: Run the pump for 8-12 hours daily to filter the entire pool volume.
• Reduces Algae Risk: Proper filtration reduces the chance of algae turning the pool water green.

Signs of a Faulty Filtration System

• Cloudy Water: You may have a broken filter if your water is consistently cloudy.
• Debris Building up: If you notice a lot of dirt or leaves in your pool, this may be because your filtration system is not capturing contaminants properly.
• Visible Algae: The filtration system may not work properly if algae are visible on the surface even during regular maintenance.
• Loud Noises in the Pump: Loud noises here can mean a broken or struggling filtration system. We can check out your pool pump.
• Low Water Pressure: Low water pressure means the filter could be faulty.
• Small Filter Size: A small filter may struggle with the required water volume and will not clean the water well.

To keep our pool water clean and clear, we need to focus on consistent maintenance, proper chemical treatment, and proper filtration. Here are some key tips to prevent algae from growing!

Tips for Regular Maintenance and Cleaning

• Skim leaves and debris from the surface.
• Brush walls and floor to remove dirt and algae.
• Vacuum regularly to clean debris from the bottom of the pool.
• Check and clean skimmer and pump baskets to ensure good water flow.

Chemicals to Use to Prevent Algae

• Test water for pH and chlorine regularly.
• Keep chlorine levels between 1-3 ppm to control algae.
• Shock the pool with a high dose of chlorine if levels drop.
• Keep pH between 7.2 and 7.6 to maximize sanitizer effectiveness.
• Use algaecides, especially during warm months.

Water Circulation and Filtration

• Run the pool pump for 8-12 hours daily to distribute chemicals evenly.
• Clean or replace filters regularly to remove debris and contaminants.
• If algae is an issue, extend filter runtime for better water clarity.
• Backwash the filter occasionally to maintain filtration efficiency.

Salt Level & Copper Algaecide Tips

• Salt Level: In saltwater pools, keeping the salt level within the recommended range allows the salt cell to produce chlorine effectively. Regularly monitor the salt level and clean the salt cell to prevent a green pool.
  
• Copper Algaecide: Copper-based algaecides, like Pool RX, work alongside chlorine to prevent algae growth. Copper is a natural algae deterrent and adds an extra layer of protection to keep your pool clear.

Stop Your Pool from Turning Green for Good

Green pools can be caused by algae growth, low chlorine, and poor filtration. Regular water testing, chemical maintenance, and proper filtration are essential to clear and clean water. Running the filter for several hours daily will prevent algae buildup.

If the pool turns green, it’s time to call a professional. A pool service company can perform thorough maintenance and treatment to restore your pool. Weekly pool maintenance can prevent 95% of algae-related problems. Our Green to Clean service is designed to restore your water fast. We provide rapid recovery services in Pflugerville, Round Rock, and Georgetown. Call us to clear it up!