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In summer, it's not uncommon for pool water to turn green. There are several reasons for this. It can be the result of particular climatic conditions (heatwave, rain/storms) that alter the balance of the water. Similarly, poor maintenance or filtration can lead to the development of green algae. In this article, you'll find practical advice on how to restore clear water with the right treatments such as flocculant and maintenance tips.
If you wonder what causes your pool water to turn green, you should know that it can have a number of different causes. It could be meteorological factors, technical causes linked to your equipment, or a human factor (natural pollution from swimming). Also, the presence of large numbers of insects - or larvae - can alter the color of the water. Please read our article how to get rid of insects in the pool.
When restarting your pool after an active wintering period, it's very common for the water to be green, so there's nothing to worry about. In this case, a proper restarting your pool should be enough to solve the problem.
During a heatwave, the water in your swimming pool overheats without cooling down during the night, thanks to the sun's UV rays. As soon as the water temperature rises above 28°C, bacteria multiply. The water then turns green. Pool walls become slippery. Without rapid action, green algae will appear. React as soon as the water becomes cloudy!
Rainwater is loaded with fine particles such as pollen, dust and sand. What's more, it has a pH between 5 and 6, whereas your pool water is balanced between 7 and 7.4.
Faulty filtration due to pump problems or clogged filters is responsible for 80% of green water. Secondly, too short a filtration time also alters the balance of the water, which will turn green before algae develop. That's why it's important to know how much time you need to activate filtration !
Leaves, sand, pollen... the water in your pond is full of dirt, especially if it's outdoors! That's why you need to regularly check the water's balance ,and disinfectant power, and clean it regularly.
The more bathers there are in a pool, the more the water deteriorates. Sunscreen, sweating...the water is rapidly polluted by the presence of bathers, who bring in organic matter. A quick rinse before diving in can help slow down changes in water quality.
When the water is green or cloudy, swimming is not recommended. This means that your pool water is polluted and full of bacteria. Ears, nose and eyes can become irritated or infected (ear infections, conjunctivitis), and this can trigger skin diseases.
As soon as the water in your pool starts to turn green, don't delay! The first step is to stop swimming until the water is healthy and clean again. The longer you wait, the more you'll need expensive chemical treatments that will deprive you of swimming.
If you notice that the walls are slippery or even slimy, algae growth has already begun. In this case, flocculant, which is an anti-algae agent, will enable you to eradicate algae. This product improves filter performance and the effectiveness of treatment and disinfection products. However, this product must not be used with diatomaceous earth filters, and cartridge filters require a specific flocculant. Finally, remember to check that your usual maintenance products do not already contain flocculant, as some of them do.
It's possible that your pool water is turning crystal green, with no algae. This problem can arise after adding a lot of disinfectant, or from water that's too acidic, or too low in TH.
Finally, if you use a TDS sensor in your salt water chlorinator pool, you don't need to measure TAC or TH. Simply check TDS measurements. Find out more about TH, TAC and TDS by clicking on the image to access our video.
Start by checking the pH of the water every day to measure its balance. If the pH is too far outside the required range, it may be necessary to apply shock chlorine to restore clarity, or simply add a pH-correcting product (pH+ or pH-). Once the product has been added, activate filtration, respecting the following rule: water temperature divided by two = filtration time. If your pool water is still not perfect after filtration, you can use a flocculant while continuing to filter the water.
If your pool is very exposed to the sun, this problem is likely to recur throughout the season. That's why it's important to protect the water as much as possible with umbrellas and shade sails, to prevent its quality from deteriorating rapidly. This will also slow down the bacteria growth process.
The first thing to do after a heavy downpour is to measure and correct the pH of the water, which is likely to be below 7 (due to the acidity of rainwater).Secondly measure the alkalinity (TAC) of the water as well as the ORP, which indicates the level of disinfection of the water. Last but not least, there's a pool water analyzer that measures the water's disinfecting power on a daily basis.
Your pool water was green or cloudy, and you proceeded to a shock treatment that clarified the water. But it lasted very shortly before the pool water turned green. The pH may be over-stabilized. It no longer has any disinfectant effect which made the shock treatment ineffective. Unfortunately, there is nothing else to do in this case than to empty 1/3 of the pool water to renew it. To confirm an over-stabilization of the water, you can perform a test with a stabilizer strip. An acceptable level of stabilizer is between 25 and 50 ppm (or mg/l). If the test you have done indicates a rate beyond this threshold, you have no other solution than to renew part of the water in
Now that you know what triggers a greenish pool, you can prevent the phenomenon. In high season, proper filtration and the creation of shade (sunshades) help to lower the water temperature. Water control and regular pool maintenance are essential.Don't forget that regular pool maintenance reduces the risk of water changes. Follow our tips to care of your pool step by step to maintain optimum water quality all season long. Swimming all summer long!
