Causes of Green Water
Green water can be caused by a variety of factors. If water samples reveal deficient levels of chlorine, this is probably the culprit. If not, you should check the iron and copper levels in the pool. Copper levels above 1 part per million (ppm) can cause blue-green water, as well as staining of hair, nails and pool walls. Iron levels above .3 parts per million can also result in green water.
If chemical tests come back fine, you might be dealing with green algae. Whereas a copper imbalance will result in blue-green, clear water, cloudy green water is probably caused by green algae. It may also cause green spots on rough areas of the pool surface.
Prevent green pool water with good pool maintenance. Monitor pH and chlorine levels regularly to prevent algae bloom, which is common in pools with high pH and low chlorine. Metal sequestering agents are usually used to treat green water that is the result of iron or copper imbalance. They are available in granular or liquid form. Always follow manufacturers instructions carefully to avoid further complications.