Green Pool: How to Fix It in 48 Hours
Opening your pool and finding the water completely green is one of the most frustrating situations for any pool owner. However, in most cases, this problem can be completely resolved within 48 hours with the right treatment. We’ll explain why it happens, how to deal with it effectively, and what to do to prevent it from happening again.
Why Does Pool Water Turn Green?
The green color is caused by algae, photosynthetic microorganisms that proliferate when the right conditions are present: water temperature above 18 degrees, sunlight, a high pH above 7.8, and an insufficient chlorine level below 0.5 ppm. The most common causes include neglecting maintenance during the height of summer, heavy rain that dilutes the chlorine and raises the pH, very high water temperatures that accelerate chlorine consumption, or a clogged sand filter that isn’t filtering properly.
Step-by-Step Emergency Treatment
At the start, perform an initial assessment. If the water is green but you can see the bottom, the problem has been developing for 24 to 48 hours. If it is completely opaque, it may have been developing for 3 to 5 days. Measure the pH before beginning.
In Step 1, adjust the pH to between 7.0 and 7.2 to maximize the effectiveness of the chlorine. A high pH makes chlorine practically ineffective. Use a pH reducer according to the manufacturer’s instructions.
In step 2, apply a chlorine shock treatment at a rate of 10 to 20 grams per cubic meter—double or triple the usual dose. For a 48-cubic-meter pool, you’ll need between 480 grams and 1 kilogram of 70% granular chlorine. Distribute the product throughout the water while the filter is running.
In step 3, run the filter continuously for the next 24 hours and backwash it every 6 to 8 hours to remove the accumulated dead algae. Filtration is just as important as the chemical shock treatment.
In Step 4, after 12 hours, add liquid flocculant at a rate of 500 ml per 50 cubic meters to agglomerate the dead algae particles into flakes that the filter can more easily trap.
After 24 hours, the water should be turning from green to a cloudy white or grayish color, indicating that the algae are dead but still in suspension. Continue filtering and backwashing. After 36 to 48 hours, the water should be clear or very close to being clear. If not, repeat the chlorine shock treatment.
When green water is a symptom of a more serious problem
If the water repeatedly turns green within a few days despite proper treatment, this may indicate an active leak introducing groundwater containing nutrients that feed the algae, an undersized filter, or a pool liner with deteriorated seams where algae find a permanent refuge.
Reinforced pool liners significantly prevent algae problems thanks to their completely smooth, seamless surface. If your pool has recurring green water issues or you suspect leaks, contact our team for a comprehensive leak detection and waterproofing assessment that can permanently resolve the problem.
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