What LSI actually measures
The Langelier Saturation Index is a single number that combines pH, temperature, calcium hardness, total alkalinity, and cyanuric acid to answer one question: is this water hungry, satisfied, or overloaded with calcium carbonate?
Between roughly -0.3 and +0.3, water is satisfied and leaves your surfaces alone. Below that, it is hungry and pulls calcium out of plaster, grout, tile, and pebble. Above it, calcium falls out of solution as scale on tile, heaters, and salt cells.
Why chasing a single number fails
Most homeowners are taught to chase pH to 7.5 and stop there. But pH is only one of five inputs. A pool at 7.5 with soft water and cold winter temperatures can be strongly aggressive, while the same pH in August with high calcium can scale a heater.
That is why Texas pools frequently show etching or roughness on plaster within a few years even though the owner tested weekly. The tests were fine. The index was not.
How we handle it
Every visit gets digital readings of your core levels rather than an eyeballed test strip, and the numbers are run against LSI before anything is added.
That means chemicals get added because the water needs them, not on a fixed schedule. It is slower to do and it is the entire reason surfaces and equipment last longer.
