What is it?

A greasy coating on the walls along the waterline of the pool is evidence that there is a saturation of undissolved materials in the water while a ring of rough patches may be a sign of scale. Most of the time, oils, lotions and other organic contaminants that enter the water via swimmers cause the greasy build-up. Scale conditions are due to hard water problems or failure to correct water balance issues. Please visit the Scale troubleshooting​ section for more info on that problem.