What Grains Per Gallon Hardness Actually Means

What Grains Per Gallon Hardness Actually Means

Let's be Clear about Grains Per Gallons Hardness

So if you are like most people you are trying to learn everything you can about your water before you decide what treatment to buy. You are not a water treatment professional so you need to dig hard to find answers and meaning to all the information about your water. You might be asking yourself what does grains per gallon actually mean?

If you get your water tested to find out the hardness mineral concentration then you will likely get the results expressed in a unit of measure known as a grain and written as grains per gallon, gpg or just grains. Want to know what that actually means?

Let's Start With Some facts:

  • The origin of a "grain" dates back to 13th century England.
  • A Grain is a real thing. You can see it, feel it and even weigh it.
  • A Grain is unit of measurement originally based on a single grain of cereal.
  • Now a Grain is a standard unit of measure and is equivalent to 0.0648 grams (g).
  • 1 grain per gallon hardness = 17.1 ppm (mg/L).
  • 7,000 grains = 1 pound.
  • 10 grain water will have 1 pound of calcium and magnesium (hardness minerals) in 700 gallons of water.

A brief history of the Grain

In the 13th century England merchants buying and selling valuable goods used a balance beam scale to determine the mass or weight of the item they were buying or selling, something like spices for instance. This was a time before modern standards of mass. Long before standards such as the gram or ounce existed merchants used grains of cereal to measure mass. They would place the object they were buying, selling or trading on one side of a balance beam and a number of cereal grains on the other till the beam balanced. The number of grains it took to balance the scale was the mass or weight of the item for trade and a transaction could then be negotiated. It wasn't an ideal way to do business but it was the best traders had at the time.

In today's more precise world we no longer use grains of cereal. We have agreed upon standard units of mass eliminating the variability between types of cereal grains and sizes within the types.

Water treatment is not the only place where the grain is still used in modern society. Next time you buy aspirin or other medicines take a look at the label, notice the term grain is used to define the amount of active ingredient. As a standard unit the grain is equivalent to 0.0648 grams and 17.1 parts per million. 7,000 grains equals 1 pound.

What does Grains Per Gallon in your water actually mean?

If you visualize a 1 cereal grain such as a grain of rice all ground up into a very fine powder like substance and dissolved in 1 gallon of your water your water will have 1 grain per gallon. Just like the medicine example, grains per gallon hardness tells us how much calcium and magnesium a gallon of water has in it. That is exactly what a grain per gallon is, the mass of dissolved hardness minerals in your water.

This means that if your water test shows you have 10 grains per gallon you have the equivalent mass of 10 ground up grains of cereal in every gallon of your water. Looking at this another way; If a gallon of your water has 10 grains of minerals dissolved in it and you let the gallon completely evaporate you will have 10 grains of mineral left in the container. This is what causes the white evaporative spotting common with hard water. This is what causes so embarrassment and many other problems costing so much time and money. This untreated hard water mineral spotting is what you have to work so hard to remove when cleaning.


Find your filter fit

Use our short product quiz to find our best fit treatment for your personal needs.

Filter Finder Quiz