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Water Hardness

Hardness in water is usually observed by its ability to form scale and make suds with soaps and detergents. If your water leaves deposits in sinks and tubs, then it is moderately hard to hard. If you get lots of suds with soap, then the water is soft. Water hardness varies across the country and around the world.

Denver’s water is slightly harder in the winter, when many lakes and streams freeze. It is softer during late spring through fall, when the snow melts and causes runoff that makes its way into the reservoirs.


Hardness in water is defined as the sum of the calcium and magnesium concentrations, expressed as calcium carbonate. The hardness of the water varies with the amounts of these salts. It is no longer an issue with laundry since most modern detergents contain water softeners.


The earth's terrain is rich in mineral content. Subterranean and surface waters absorb some of these minerals. Absorbed minerals include compounds of calcium and magnesium carbonates, bicarbonates, sulfates and chlorides. These naturally occurring minerals give water its hardness.


Very hard water can leave a chalky or mineral aftertaste. Water that is too soft leaves a flat, unpleasant taste. A balance needs to be maintained. Hardness versus softness are not health concerns, but aesthetic ones. Our goal is not only to maintain a safe product, but also one that tastes, smells and looks good.


Denver's water tends to form scale. An initial scale usually takes two to five years to form and continues to build up over time. In older areas, while thick scale reduces rate of flow, it prevents water from being in contact with the plumbing. This protects pipes from corrosion and customers from potentially harmful metals. When using a cold water humidifier, hardness in the water can cause residue deposits on furniture. Deposits can be minimized by using half tap water and half distilled water in the humidifier.