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Converting Water Hardness Values
December 28, 2023 1 min read
Water hardness can be expressed a number of different ways, and it's often important to know how to convert one unit to another for the purposes of selecting and properly programming water softeners. Here are the common ways water hardness is expressed and how to convert values in one unit to another:
Common Water Hardness Units:
mg/L - this is commonly encountered on lab reports
ppm - also seen on lab reports and is exactly the same as mg/L
GPG - "grains per gallon" often used by retailers and equipment manufacturers
To convert from mg/L or ppm to GPG divide the hardness value by 17.1
Here are examples:
200 mg/L / 17.1 = 11.7 GPG
450 ppm / 17.1 = 26.3 GPG
To convert from GPG to mg/L or ppm, multiply the hardness value by 17.1
Here's an example:
15 GPG x 17.1 = 256.5 mg/L (or ppm)