What does a negative Langelier Index value suggest about water?

A negative Langelier Index value indicates that the water is corrosive. The Langelier Index measures the saturation state of calcium carbonate in water and helps predict whether water will tend to either deposit scale or dissolve materials. When the index is negative, it suggests that the water is not saturated with calcium carbonate, which means it has the potential to dissolve calcium carbonate from pipes, fixtures, or any surfaces it comes into contact with.

Corrosiveness in this context can lead to leaching of metals from plumbing systems, which can pose health risks if heavy metals like lead or copper enter the drinking water supply, making this information critical for ensuring safe drinking water quality.