Langelier Saturation Index

Decades ago, people in the pool industry started becoming aware that there was more to pool maintenance than just adding sanitizers to the water (to kill algae and bacteria) and filtering it (to help keep it crystal clear).  Gradually, we learned that even properly sanitized and filtered pool water could become unbalanced.   Further, we figured out that unbalanced water could be either scale-forming, in which case a layer of