Why Is My Pool Green & How Can I Fix It?
A pool turns green primarily due to algae growth, which thrives when certain conditions in the pool are favorable. Here's a breakdown of why this happens and how to fix it:
1. Low Chlorine Levels
Chlorine is the primary sanitizer that prevents algae from growing. If chlorine levels fall below the recommended range (1–3 ppm), algae can grow unchecked.
Causes of low chlorine include:
Poor maintenance or neglect.
Heavy rainfall diluting chlorine levels.
High pool usage consuming available chlorine.
Solution: Shock the pool with chlorine to kill algae and restore sanitizer levels. Maintain regular testing to ensure consistent chlorine levels.
2. Imbalanced Water Chemistry
High pH Levels: When pH rises above 7.6, chlorine becomes less effective, allowing algae to thrive.
High Alkalinity: Elevated alkalinity can cause scaling and disrupt sanitizer efficiency.
Solution: Test and adjust pH levels to the ideal range (7.2–7.6) and keep alkalinity between 80–120 ppm.
3. Poor Filtration and Circulation
Insufficient Filtration: If your filter isn't working properly, debris and algae spores can remain in the pool.
Short Filtration Times: Running the filter for fewer than 8–12 hours a day may not allow for proper water turnover.
Dead Spots: Poor circulation in corners or around steps allows algae to grow undisturbed.
Solution: Ensure your filter is clean and functioning properly, and run it for adequate periods. Use pool brushes to scrub areas with poor circulation.
4. Warm Temperatures and Sunlight
Warm Weather: Algae flourish in warm water, especially during summer.
UV Exposure: Sunlight breaks down chlorine, reducing its effectiveness.
Solution: Use a pool cover to limit sunlight exposure when the pool is not in use. Add a chlorine stabilizer (cyanuric acid) to protect chlorine from UV degradation.
5. Introduction of Algae Spores
Environmental Factors: Rain, wind, and debris can introduce algae spores into the pool.
Swimmer Contamination: Algae can hitch a ride on swimsuits or pool equipment from other bodies of water.
Solution: Clean pool toys and equipment before use and encourage swimmers to rinse off before entering the pool.
6. High Phosphate or Nitrate Levels
Phosphates and nitrates act as nutrients for algae, fueling their growth. These can enter the pool through fertilizers, decaying leaves, or rainwater runoff.
Solution: Use a phosphate remover and regularly skim and vacuum the pool to remove organic debris.
How to Treat a Green Pool
Shock the Pool: Add a high dose of chlorine or algaecide to kill algae. Follow product instructions for dosages.
Brush and Vacuum: Scrub pool surfaces and vacuum debris to remove dead algae.
Run the Filter Continuously: Operate the filtration system until the water clears.
Retest Water Chemistry: Balance pH, chlorine, and other chemical levels to prevent recurrence.
Preventing a Green Pool
Test water chemistry 2–3 times per week.
Maintain consistent chlorine levels (1–3 ppm).
Run the filter daily for 8–12 hours.
Clean the pool regularly to remove debris.
Use preventative algaecides in high-risk seasons (e.g., summer).
By addressing and preventing the factors that cause algae growth, you can keep your pool clean, clear, and inviting.