Hard water is probably the most common water problem found in the home. Water described as “hard” is high in dissolved minerals, specifically calcium and magnesium. As water moves through soil and rock, it dissolves very small amounts of minerals and holds them in solution. Calcium and magnesium dissolved in water are the two most common minerals that make water “hard”. The degree of hardness becomes greater as the calcium and magnesium content increases. Hard water is not a health risk; in fact, it’s mineral content makes it healthy for your body, but a nuisance to your home because of the mineral buildup on plumbing, fixtures, and poor soap and/or detergent performance.
- Soft water – less than 1 grain per gallon
- Slightly hard – 1 to 3.5 grains per gallon
- Moderately hard – 3.5 to 7 grains per gallon
- Hard – 7 to 10.5 grains per gallon
- Very hard – 10.5 and higher grains per gallon
What Does Grains Per Gallon Or GPG Mean?
Parts per million or grains per gallon are both used to describe the dissolved hardness minerals contained in the water. One part per million (PPM) is one of a substance out of one million units of water. A grain, or grains per gallon (GPG), is a unit of weight. It is 1/7000 of a pound. One GPG, (1gpg) is equal to 17.1 PPM.