Definition - What does Grains mean?
Grains, in terms of water hardness measurement, refer to the unit of weight that is equivalent to 1/7000th of a pound.
In an average household with four members, a water hardness level of approximately 7 grains per gallon (gpg) is equivalent to 66 kilograms of rock in the water per year.
Corrosionpedia explains Grains
One application of the unit "grain" is in the measurement of water hardness, which is measured in grains per gallon or Clark degrees. In a more detailed sense, grains per gallon can be described as one part of grain per 58,000 parts of water.
Water is considered soft as it falls as rain. However, it collects particles like magnesium, calcium, lead, iron, etc. as it passes through soil and rocks. Due to the high grain levels per parts of water, some abilities are reduced, like the ability to clean and produce soap suds. Grainy water also leaves stains and impurities on clothes, dishes and other things. Additionally, hard or grainy water is more abrasive, has less capacity to heat and may cause corrosion and scale buildup on water pipes, heaters and other plumbing fixtures.
Typically, soft water has a hardness of 0-1 gpg, while very hard water has 10.5 gpg. In order to reduce water hardness, softening tanks and other chemicals are used. To maintain quality of water, water hardness should be measured, documented and reported in a timely and efficient matter. This prevents corrosivity, bad odor, undesirable color and other negative water properties.