Ryznar Stability Index (RSI)

Estimates the actual scaling or corrosive behavior of water from field observation. Values below 6 indicate a scale-forming tendency, 6 to 7 is balanced, above 7 indicates a dissolving (often corrosive) tendency.

$$\text{RSI}=2{\text{pH}}_s-\text{pH}$$

Variables

Symbol	Meaning	Unit
${\text{pH}}_s$	Saturation pH at calcium carbonate equilibrium	unitless
$\text{pH}$	Measured pH of the water	unitless

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Part of The Blueprint of Water