Green pool water? Let’s identify the causes and the solutions. Pool water turning green can be caused by a number of things, a few of which have simple solutions.
First, pool water can be green because of algae buildup. In a chlorine pool, this algae buildup can be due to a lack of appropriate amounts of chlorine in the water. You can identify algae as slimy and dark green, and it sticks to the walls and bottom of the pool. Check the pool’s filter to see if it is running properly before treating the problem. Pool water with algae buildup and/or a lack of chlorine is unsafe to swim in and may require an algicide treatment in addition to chlorine treatments. The best solution for treating algae in a chlorine pool is super-chlorinating the pool with chemical shock treatment. If the pool water is still green after shock treatment has been added, additional solutions may be needed. We will explore this in a later section.
Second, pool water can appear green due to pollen. You can identify pollen as a more yellow-green color, but unlike algae, it does not build up on the surface of the pool water. Also unlike algae, despite also turning pool water green, pollen does not make the pool water unsafe to swim in or require algicide or fungicide. Pollen can be treated by adding a flocculant to the water. A flocculant is a substance that promotes clumping together of particles, which in this case makes it easier to skim the pollen particles out or causes them to get picked up by the pool filter. Again, before adding treatments to the pool, check the chlorine levels in the pool and check to ensure that the pool’s filter is running properly.
Third, pool water can be caused to turn green from metals. You can identify a metal issue by pool water’s light green color. If you have green pool water after shock treatment has been done, metals are most likely the cause of the problem. With metals causing the pool to be green, this is a sign that the alkaline levels/pH balance is off. This means that there is a chemical imbalance not necessarily affected by the amount of chlorine in the water. After you have identified that the problem was due to low pH/alkaline levels in the water, you can add sequestrants to the water. Like flocculents discussed earlier in treating pollen in pool water, sequestrants will group metal particles together to allow them to more easily be caught by the pool’s filter or by pool skimmers. After treating with sequestrants and removing the metals from the pool water, if you determine that the pH/alkaline levels are still low, this could mean that the source of the metals is coming from the source water. In this case, treat with sequestrants regularly to keep the metals filtered out of the water on a weekly basis.
In conclusion, algae and pollen are common causes of green pool water in chlorine pools and are treated by super-chlorinating the pool or adding chemicals to group particles together and filter them out. If your pool is turning green even after shock treating (super-chlorinating) the pool, metals are likely the cause. Don’t feel healthy or safe treating your pool with super-chlorination or other chemicals regularly to keep it from turning green? Explore non-chlorinated pool options.