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A Breakdown of the Water Hardness Scale

If you have hard water you probably want to know exactly how hard your water is. To do so, you’ll have to test the mineral content of your drinking water. Understanding what the mineral content of your water means requires an introduction to water hardness levels, and then comparing your results with a water hardness scale. In this article, you will learn about the difference between hard water vs. soft water and see how it can affect your tap water at home.

What is Water Hardness?

Water hardness is the concept used to communicate how much or how little dissolved minerals a sample of water contains. Water is considered “hard” if it has relatively high levels of dissolved minerals, the most common of which are calcium and magnesium. Water with very low levels of dissolved minerals is considered “soft”. To attain “soft” water, many people consider installing a water softener. So what is a water softener exactly? A home water softener system decreases the hardness of water, resulting in softer water.

What is the Water Hardness Scale?

Now, you must know that drinking water isn’t considered either hard or soft. Rather, water hardness is a sliding scale that is used to tell exactly how hard water is. Water can have only trace amounts of dissolved minerals, or be saturated in dissolved minerals, with water of varying degrees of hardness existing in between.

The water hardness scale is used to define the specific hardness of water. The scale can help you understand how hard your tap water is in relation to other water hardness readings, and to make an informed decision about whether you need a water softening solution in your home or business.

How to Use the Water Hardness Scale?

In order to determine your water hardness, you first have to take a sample of your water and measure its mineral content. You can use a test kit to measure the mineral and calcium hardness in your tap water. The most common water hardness tests measure this mineral content in grains per gallon (GPG). Specifically, your hardness test will let you know the GPG of calcium carbonate that a sample of water contains. This measurement is then applied to the water hardness level scale to determine how hard or soft your water is.

Here is the most common scale used to determine the dissolved mineral content of your water supply:

  • Water is considered soft if it contains less than 1 GPG of dissolved minerals.
  • Water is considered moderately hard if it contains between 1 – 7 GPG of dissolved minerals.
  • Water is considered hard if it contains between 7 – 10 GPG of dissolved minerals.
  • Water is considered very hard if it contains more than 10 GPG of dissolved minerals.

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Why is Water Hardness Important?

Understanding whether you have hard water, and how hard your water is, can help you take steps towards combating the impact of hard water. But why bother finding out if you have hard water in the first place? Most people want to know because hard water can have a number of detrimental effects to your water supply. Some of these you may already be familiar with, even if you didn’t know what caused them.

Here are some of the most common signs of hard water around the house:

  • Mineral Deposits – When hard water comes in contact with surfaces around your house, it will leave behind mineral deposits. These mineral deposits are often whitish in appearance and can be difficult to remove. You’ll commonly see mineral deposits on surfaces and fixtures, on nozzles like your shower head, and on your dishes and cookware.
  • Soap Scum – Soap scum is a whitish or yellowish substance that forms from a reaction by the minerals in hard water with soap. The result of this reaction is an insoluble precipitate that stubbornly coats surfaces it comes into contact with. Soap scum can serve as a breeding ground for mold and mildew and will return quickly despite frequent cleaning.
  • Brittle Hair – Hair that is washed in hard water is less strong than hair washed in soft water. The minerals in hard water penetrate the hair follicle, causing it to weaken over time. At the same time, washing your hair with shampoo and conditioner will be less effective because the minerals won’t allow them to penetrate the hair follicle. The mineral deposits will also weigh down hair, giving it a flat and dull appearance. 
  • Faded Clothing – Clothing washed in hard water will lose its color faster due to a buildup of mineral deposits on the fabric. The minerals left behind by hard water will also weaken the structure of the fabric with each washing, causing it to become more brittle and wear out more quickly.

Closing Thoughts

The effects of hard water are widespread and quickly become frustrating. The first step towards addressing the effects of hard water is to understand how hard your water is through a water hardness test kit. The water hardness scale is used to help us understand if a sample of water is hard, and exactly how hard that water is.

The water hardness scale can provide context for a water hardness measurement. Typically, hard water is measured in terms of grains per gallon (GPG) of dissolved minerals the sample contains. Without the context that the water hardness scale provides, this measurement is simply a number. Once applied to the water hardness scale, this measurement can tell you how hard your water is relative to other water supplies. Once you have used a test kit to measure your calcium hardness, you can then improve your hardness level with a water softening treatment.

If you’re looking for a water filtration system to have purified water in your home, Rayne can help. To learn about an innovative solution to hard water such as a water softening treatment, please contact Rayne today.


  3. Ungvarsky, Janine. “Hard Water.” Salem Press Encyclopedia of Science, 2018.
  4. Luqman, Muhammad Waqas, Muhammad Haris Ramzan, Usama Javaid, Roshan Ali, Muhammad Shoaib, and Muhammad Ayyas Luqman. “To Evaluate and Compare Changes in Baseline Strength of Hairs after Treating Them with Deionized Water and Hard Water and Its Role in Hair Breakage.” International Journal of Trichology 10, no. 3 (May 2018): 113–17.