Aquatell, Inc Blog Converting Water Hardness Values

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)