What is Grains Per Gallon Hardness?
The high-level answer is this; Grains Per Gallon hardness (abbreviated as GPG) is a standard expression of the concentration of hard water minerals in your water. Furthermore, it is a unit of mass or weight. If the mineral concentration of your water is measured in parts per million or milligrams per liter you can convert to GPG by multiplying by 17.1.
What does a Grain Per Gallon Hardness look like?
Image a grain of rice, it's roughly the mass of 1 Grain and is a great way to visualize how big a Grain is.
Now here's a fun fact; If a gallon of water containing 10 grains hardness were to evaporate or be boiled till gone there would be a mass of hardness minerals equal to 10 grains of rice left in the container.
Another visual; if you’ve got 1,000 GPG of calcium in your water, then you’ve got about a quarter cup of calcium in every gallon of water.
How Does a High Grain Per Gallon Hardness Affect Me?
If not removed or treated to change the way the hardness mineral behaves a high GPG translates directly to all the things we dislike about hard water simply being worse. Higher the GPG the worse the hardness problem you'll experience.
Knowing the GPG mineral concentration in your water is an important factor in determining the best way to treat it. At the end of the day, you should have the right treatment (including the right amount of that treatment) for the right water problem.
What GPG is OK?
This is a common question we get when people begin to learn about GPG hardness. According to the Water Quality Association you will experience hard water problems when the concentration of hardness minerals is measured to be 3 GPG or higher. We suggest you let the symptoms be your guide.