Hard Water and How It Damages Plumbing - The Spruce Water hardness is commonly measured in milligrams per liter (mgL) or grains of mineral per gallon (GPG). Definition Measurement m Water hardness is quantified by the concentration of calcium and magnesium ions in the water. Hard water is any water containing a substantial quantity of dissolved minerals. Water hardness is most often expressed in grains per gallon (gpg but you may also see it as parts per million (ppm).
The Water Hardness Scale How Hard is Your Water? Hard Water by the Numbers in GPG - HomeWater1Water hardness can be measured in gpg or ppm, but gpg is the most commonly used measurement. Water Hardness Chart for Water Treatment Equipment Extremely Hard Water 1 GPG (total grains x 1 equals ppm) WARNING : Beware of companies that tell you that each PPM of iron is equal to 4-Grains per gallon of hardness.