"Hardness" is a property of water determined by the amounts of dissolved minerals it contains, specifically calcium and magnesium. Most people associate the term with water quality and also with a build-up of material in their shower or sink. This accumulation occurs because soapsuds can’t be produced until dissolved minerals in the water have been combined with soap. Those minerals that are removed from the water remain as an insoluble residue.
Water hardness is generally the highest in groundwater where the topsoil is thick and carbonate formations are present. As rain falls, it absorbs carbon dioxide produced from bacteria in the topsoil. The rainwater and carbon dioxide mix to form carbonic acid. Carbonic acid dissolves the carbonate compounds found in limestone and dolomite. This process is enhanced by acid rain. The degree of hardness increases as the calcium and magnesium amount increases and is related to the concentration of multivalent cations dissolved in the water.
Water hardness is a relative term and typically reported in milligrams per liter (mg/L) of calcium carbonate (CaCO3), or grains per gallon (gpg).
|
Relative Hardness |
Mg/L |
gpg |
|
Soft |
0 - 60 mg/L |
0 - 3.5 gpg |
|
Moderately Hard |
60 - 120 mg/L |
3.5 - 7 gpg |
|
Hard |
120 - 180 mg/L |
7 - 10.5 gpg |
|
Very Hard |
Over 180 mg/L |
Over 10.5 gpg |
Colorado Springs Utilities reports a hardness measurement of 1.3 – 2.8 grains per gallon (gpg), which gives its water a relatively soft rating. For comparison, Denver has a reported 4.2 gpg and the city of Pueblo has the state's hardest water at 10.6 gpg.
In an example on the far end of the spectrum, London's water is derived mainly from the River Thames and River Lea, which draw a significant proportion of their dry weather flow from springs and limestone aquifers. Consequently, drinking water there is very hard with 11.7 gpg of calcium carbonate.
Here in the U.S., people living in areas like Pueblo can use water softeners that replace the calcium and magnesium content of hard water with sodium. Plasticizers are another method of converting hard water into soft water. The process uses sodium, calcium, magnesium, manganese, and iron, which are dissolved to reduce calcium or magnesium.
Although treating hard water with salt and a water softener is common, most people don't know that if you use one of these devices, you are basically removing calcium and magnesium from your drinking water and adding salt to your diet. In addition, water softeners can be expensive to install, and many states actually have banned the use of salt softeners because of their harmful effects on the environment.
Hard water is not hazardous to your health, but it can be a nuisance. If you’re looking for alternative drinking water sources for your home or have questions about your home water as a Colorado resident, contact the Eldorado team. We're always happy to share our insights and help people get the high-quality drinking water they need to stay hydrated!