Staff Answer
Jul 17, 2026 - 10:08 AM
A salt chlorine generator is designed to maintain clean water, but if something causes the chlorine demand (how much chlorination the water requires to stay clean and clear) exceeds how quickly the system is generating chlorine, it can lead to an algae infestation.
The reasons why it happened can vary, examples: they system wasn't running at a high enough output setting / long enough during the day, an error light may have triggered and stopped chlorination until the issue was fixed, organic matter / waste / impurities might have gotten into the water, water chemistry may have become imbalanced to make chlorine ineffective or to boost microorganism growth, and more.
Use a recent water chemistry report and ensure all levels are balanced, focusing on achieving and maintaining 7.2 pH and a super-chlorination level for free chlorine in the water continuously until all algae has been killed and removed from the pool and pool system. To do so, use liquid chlorine or another pool shock; how high to raise and continuously maintain the free-chlorine level will be based on your CYA level (the higher your CYA, the higher the free-chlorine level you need to achieve). Brush all pool surfaces thoroughly, vacuum debris, run the pump and filter continuously, and clean or backwash the filter as needed. Continue until the water is clear, there is no visible algae, and the pool holds its chlorine level overnight. Popular approaches include the SLAM method, which you can find online.
Also check for poor circulation, clogged filters, shaded areas, ladders, light niches, and other locations where algae can remain. Once the infestation is eliminated, return the salt system to normal operation and adjust its output or pump runtime so it maintains the proper daily chlorine level.
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