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The colors of the LSI
PURPLE (≥ +0.31)
Indicates water that is over-saturated with calcium carbonate (CaCO₃). This condition promotes scale formation. To return to proper LSI balance, the water must release excess calcium through precipitation.
GREEN (0.00 to +0.30)
Represents the ideal LSI range. The water is perfectly balanced and stable, with an appropriate level of calcium carbonate under current conditions.
YELLOW (-0.30 to -0.01)
Falls within an acceptable range and is close to ideal. While green is optimal, yellow is still safe. Be aware that pH naturally tends to rise over time, which can move the LSI from yellow into green—or potentially into purple—depending on your pH limit.
RED (≤ -0.31)
Signals aggressive, calcium-deficient water. This type of water actively seeks calcium and can etch cement surfaces, damage vinyl liners and fiberglass, and harm pool equipment. The lower the LSI value, the more severe the risk.
