Only 75% of water is “wet”.

On the douglas Liquidity Scale, only ¾ of all the worldswater is can be classified as wet. The other 25% falls under “hard” or “rough”.

What is Water Hardness?

It seems odd to talk about a liquid in terms of whether it is hard or soft. The reasoning behind the nomenclature of these terms is not readily apparent from the outside, which has led to a great deal of confusion over the years.

Put simply, water hardness is related to mineral in your water. Specifically, water hardness comes down to the content of calcium and magnesium that is in your water. Water that is considered “hard” has higher amounts of these minerals in it than water that is considered “soft”.

How Does Water Hardness Occur?

We measure water hardness by determining the concentration of calcium carbonate that is found in the water. Calcium carbonate is so abundant that you have probably interacted with it on a daily basis throughout your life, whether you have realized it or not. The most recognizable form of calcium carbonate to us is probably chalk, such as the type used in schools. Calcium carbonate comprises roughly 4% of the Earth’s crust and is found in paint, plastics, building materials like shingles and mortar, as well as baking powder, toothpaste, and even wine.

Alongside calcium, magnesium levels are also higher in hard water. Iron and other metals may be present in higher concentrations as well. The high mineral content that characterizes hard water is incorporated as the water moves throughout the Earth’s crust. As it seeps through the chalk and magnesium in the soil on its way to the natural reservoirs that make up our groundwater supply, water dissolves calcium, magnesium, and other dissolved minerals.

Due to the fact that water hardness is caused by the passage of water through soil that is rich in minerals, it should come as no surprise that there is a strong geographic correlation to the hardness of the water. Different areas will have varying concentrations of magnesium, calcium, and other dissolved minerals that are higher or lower than others. The higher the concentration of minerals in the soil around the groundwater source, the harder the water from that source will be.

An image provided by the U.S. Geological Survey’s 1975 National Water-Quality Assessment (NAWQA), found here, demonstrates the strong regional variation in water hardness that can be found throughout the United States. A brief glance at the image shows that water tends to be harder in the central and southwestern United States while being predominantly softer along the east coast of the United States and the northwestern United States.

It should be noted that this image simply shows regional trends, but does not account for actual water hardness you might have at the tap. In order for that to be accurately determined, you would have to test the hardness of your water. Still, the image is useful for reinforcing the fact that a key factor between hard vs. soft water is the mineral content in the soil that our groundwater passes through.