Comparing Langelier Saturation Index, Aggressive Index, and Ryznar Stability Index
There are several methods to measure how likely a water source is to either cause scale or be corrosive. These are Langelier Saturation Index (LSI), Aggressive Index (AI), or Ryznar Stability Index (RSI). In this article we’ll explain what each one is, how they differ, and what it means for your home’s water quality.
What is “Aggressive” Water?
When it comes to measuring water quality, aggressive water means it is under-saturated with minerals, making it corrosive. Corrosive water can damage pipes, water pumps, and appliances, shortening their lifespan. It can also cause your water to leech chemicals from your pipes.
Are there health risks to Aggressive Water?
Water does not inherently become unsafe because of aggressive water. But it does mean that your water is more likely leech metals or other chemicals from your plumbing that can have health consequences.
What is “Scaling” Water?
Scaling water is over-saturated with minerals, leading to the tendency to deposit “scale” on your appliances and plumbing. Scale can clog pipes, reduce appliance efficiency, and leave unsightly white streaks on surfaces.
Are there health risks to Scaling Water?
Scaling water is generally considered safe to drink. The primary concern with scaling water is damage to plumbing/appliances, aesthetic issues, skin dryness, and hair damage.
LSI vs RSI vs Aggressive Index
LSI vs RSI vs Aggressive Index all measure water’s tendency to corrode water. Below will show the range for each measurement.
Langelier Saturation Index
The Langelier Saturation Index (LSI) is a measurement that shows the saturation level of calcium carbonate in water. It determines how “balanced” your water is. It is measured from negative (corrosive) to positive (scaling) with any number from -0.3 to 0.3 being “balanced”.
Aggressive Index
Aggressive index is not a quantitative measurement of corrosion, but a general indicator of the tendency for corrosion to occur. Unlike LSI and RSI, Aggressive Index only measures the tendency for corrosion to occur and does not measure the likeness that water will scale. Any number that is 12 or above is nonaggressive. While lower numbers mean more aggressive.
Ryznar Stability Index
The Ryznar Stability Index is similar to the LSI, but mathematically adjusted to always be represented by a positive number. The equation used by RSI is mainly based on empirical observations of scaling and corrosion of metals in municipal water systems.
Above 7 is aggressive and below 5 is scaling. Between 5 and 7 is considered balanced.
Testing for Water Aggressiveness or Scaling
All 3 measurements of water aggressiveness are tested in our Safe Home Premium Drinking Water Test Kit. This kit measures 50 of the most important parameters for water quality and is tested at our EPA-Certified Laboratory.
FAQ About Corrosive Water
Is Scaling and Hard Water the Same thing?
Scaling and Hard Water are similar and related, but not the exact same. Hard Water simply measures the amount of dissolved minerals. While scaling accounts for water hardness, pH, and temperature. If water has high hardness, it’s more likely to leave scale.
What do I do if my water is aggressive (Corrosive)?
Increase the hardness of your water to reduce corrosiveness. Many commercial products are available to boost water hardness, particularly for pools. You will need to speak to a water filtration professional to see what system is right for your home.
What do I do if my water is prone to scaling?
A water softener can significantly reduce your water’s hardness and make it less prone to scaling. We have free tools to help you figure out what capacity water softener is needed for your home.