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Why is my pool GREEN?!

Improper pH Balance

Chlorine is a chemical added to swimming pools to kill bacteria that can build up over time and lead to a discoloration of the water. Green water is most often a sign of algae, not necessarily bacteria, but different pools have different bacteria that can affect the water. If the pH balance of the water isn’t in the right place, it will allow bacteria to flourish, leading to further discoloration. If the pH level is too low, the water is acidic and over time, it will erode plastic and metal components. A pH level that is too high will not kill bacteria and will allow scale buildup of calcium and other minerals. A healthy pool is between 7.2 and 7.8 on the pH scale.

Clogged Filter

Not all water-color issues are the fault of the water itself. For example, a filter system that isn’t working properly won’t strain out the surface algae and other debris. If left to stagnate, your pool will become a breeding ground for mold, algae and other fungi that will eventually change the color of the water. Pool filters are designed to be cleaned with buckets, baskets and filter systems that are easily disassembled. If your filter is clogged and causing a backup of color-changing water issues, clean the filter. Most pools have a system where you can simply remove the filter, clean it with water and a scrub brush, then replace it. Different pools have different filters, so always follow the manufacturer's instructions for removal and replacement of parts.


Algae thrives in warm, humid temperatures. Normal chlorine may not be enough to counter the buildup of algae within a pool, but there are special algaecides sold which are specifically designed to work against those extra-tough algae in the warmer months, when it is more prone to spread. If the pH level of your pool is good but you still have green issues, it is the result of algae buildup and the pool needs an extra dose of algae remover. Different brands have different instructions for use, but you should always start with a minimal dose and increase it, as needed.

Shock Treatment

Shock treatment is a temporary solution used when there are excessive levels of algae and other buildup in a pool which are keeping the water green or discolored, even when you are trying to keep the pH balance in check. The only solution in this case is to “shock” the pool, which involves treating the pool with a large dose of chlorine and algaecide. Allow the pool to sit for 24 hours to kill off the algae and bacteria. After 24 hours, you can clean the pool and restore the pH for continued use.

Ongoing Maintenence

The best remedy for a discolored pool is regular maintenance. This means vacuuming the bottom of the pool regularly, scrubbing the walls and vacuuming them, skimming the surface to remove debris, regularly cleaning the filter system, regularly checking the pH level and adding more chlorine. You should also add algaecides, as necessary. Pool maintenance is a full-time job that requires daily focus to keep the water crystalline and enjoyable. For best results, check the water on a daily basis to keep algae and other bacteria-related issues from becoming a problem.

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