Why Is My Pool Green?

When you picture your swimming pool, you envision a clear oasis of tranquility shining under the sun, coaxing you to take a refreshing dip at your leisure, day or night. However, this tranquility can quickly turn into a disheartening reality when the water turns into an unsettling shade of green. Pool water, being stagnant, is prone to collecting bacteria and algae if not properly maintained. Over time, these unwanted guests can significantly alter the looks and safety of your pool.

Addressing the issue of a green pool is not just about restoring its visual appeal; it's about ensuring the health and safety of everyone who uses it. The effort required to maintain the clear pool water largely depends on how long the buildup has been allowed to progress. A pinch of prevention is undoubtedly worth a pound of cure, showing the importance of understanding and preventing the causes of algae and bacteria buildup.

5 Potential Issues Why Your Pool Is Green

Discovering your pool has turned green overnight is a common experience for many pool owners. This abrupt change can be attributed to various factors, including pollen invasion, chemical imbalances boosting algae growth, or the oxidation of metals in the water. Identifying the root cause of your green pool is the first step towards a cleaner pool.

Not Enough Chlorine in the Pool

Chlorine is a powerful chemical that acts as a relentless warrior against the unseen threats of bacteria and algae, ensuring your pool remains a sanctuary of cleanliness and safety. However, when the level of chlorine drops below the necessary threshold, your pool can quickly turn green.

Test your water using pool test strips or bring it to your local pool shop to have it tested and ensure your pool's free chlorine levels are consistently maintained between 1 ppm and 3 ppm. Regular monitoring of your water chemistry not only keeps algae at bay but also secures the health and enjoyment of your pool.

Chlorine Bound by Chloramines

Chloramines are the chemical byproducts that build up in the water when it's improperly treated with too little chlorine, representing a signal that your pool's water chemistry is imbalanced and requires attention. The solution to combating chloramines and getting the clean pool back is regular water testing and a chlorine shock treatment. This process involves adding a high dose of chlorine to the water to break apart the chloramines, freeing up chlorine to effectively perform its sanitising duties. Consult with your local pool pro if you need more information, as the amount of chlorine you add will depend on the size of your pool and other factors.

High pH Level

pH measures how acidic or basic the water is, which plays a crucial role in your pool's chlorine effectiveness. Various elements can influence your pool's pH level, from weather changes to the introduction of oils, dirt, and even cosmetics. Each swimmer or environmental factor interacting with your pool can shift the pH balance, potentially leading to higher pH levels. When the pH climbs too high, it forms a protective barrier around chlorine molecules, causing the chlorine to become ineffective.

The presence of green water, despite adequate chlorine levels, often signals a pH imbalance. A pH value at or slightly above 8.0 begins to reduce chlorine's sanitising power, and it can drop even further as the pH rises further. If you are using a saltwater chlorinator, this is particularly important as saltwater chlorination leads to higher pH levels than traditional chlorination.

Not Enough Cyanuric Acid

Maintaining a sparkling pool requires attention to many details, including ensuring an adequate level of cyanuric acid (CYA). Often referred to as "sunscreen for chlorine", CYA plays a vital role in safeguarding your pool's chlorine from evaporation caused by the sun's UV rays. Without this protective layer, your pool's chlorine would rapidly reduce, leaving your water vulnerable to algae growth. Regular testing of your pool water to monitor cyanuric acid levels. You can shield your chlorine from UV degradation by ensuring these levels remain within the recommended range.

Not Enough Circulation/Filtration Time

Circulation of the pool water keeps it filtered and clean and helps spread the pool chemicals you add to the water. Think of a cup of coffee after adding cream and sugar, and it requires stirring to blend them. Same with the chlorine and CYA that go into your pool so that it will be evenly throughout.

The typical filtration time is running your pool pump for at least one hour for every 5.5 degrees of air temperature. For example, if it's 30 degrees outside, the pool pump must run for at least 10 hours daily. However, this can also be affected by weather patterns and increased swimmer load. Therefore, adjusting the operation time of your pool pump in response to these variables is crucial for maintaining water quality.

Types of Green Pools

Green and Cloudy Pool Water

If your pool water looks green and cloudy, then this is a common indication of an algae infestation. This type of green pool often arises suddenly, perhaps overnight or following a rainstorm, meaning inadequate water circulation or filtration system malfunctions. Such problems prevent the effective distribution of pool chemicals, allowing algae to thrive.

Pool Water Appears Green but Remains Clear

A pool that looks clear but with a greenish tint presents a different set of challenges. This could attributed to external factors such as pollen or chlorine-resistant algae strains. However, the most common issue behind this is an elevated pH level. When your pH level is over 7.8, even substantial chlorine concentrations lose their efficacy, failing to sanitise the water properly.

Step-by-Step on How to Fix a Green Pool

Step 1: Test Your Pool Water

Ensure your pool's pH is within the optimal range, as a balanced pH ensures the effectiveness of chlorine and shock treatments. You will also need to check alkalinity, free chlorine and phosphate levels.

Step 2: Balance pH levels and Apply Shock treatment

Balance your pH level if needed and add a superchlorinated shock treatment, adhering to the recommended dosage to prevent under-treatment. You might need to do a second shock if your pool is severely affected by algae.

Step 3: Check the filtration system for problems or malfunctions

Inspect and clean the pool filter, which may be clogged with algae remnants.

Step 4: Scrub the Floor and Walls Thoroughly

Begin by manually vacuuming the pool bottom and sides, targeting areas with noticeable algae buildup. Follow up with a stiff-bristled brush to scrub the pool floor and walls.

Step 5: Run Your Pool Filter

Operate your pool filters until the water clarity is restored, which may take several days. Consider adding a pool clarifier to accelerate the process, but allow at least 24 hours of filtration to eliminate dead algae and ensure the shock treatment is working.

Step 6: Test Your Pool Water Again, Rebalance and Monitor

After treating the pool, retest and adjust the water chemistry, and pay attention to pH, alkalinity, and chlorine levels. Regularly monitoring the pool's water chemistry is essential to avoid future algae problems.

How to Prevent My Pool Turns Green

Skim Your Pool Regularly

Use a pool net to skim leaves and floating debris from the water's surface. Quickly removing debris is far easier before it has a chance to sink and settle at the bottom of your pool.

Routine Water Testing

Test your pool water regularly by using pool testing strips weekly or bringing a sample to your local pool shop for a comprehensive analysis at least once a month. If you find an imbalance in the pool chemistry early, you can prevent minor issues from escalating into a big one.

Maintain a proper chlorine level

Ensuring chlorine levels between 1 and 3 ppm is crucial for deterring algae proliferation. Adequate chlorine levels are the cornerstone of a healthy, clean pool.

Bottom Line

While tackling a green pool can feel overwhelming, it's a manageable challenge with the correct preventative measures and prompt action. By implementing the strategies outlined above, such as regular skimming, routine water testing, and maintaining optimal chlorine levels, you're well on your way to preserving the health and clarity of your pool.

If you've already got enough on your plate, we recommend hiring a pool technician to vacuum your pool and check chemical levels regularly. Always consult with your local pool professionals if you have any persistent problems. Use our dealer locator to find your nearest pool dealer.