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The ‘hard’ truth about soft water

Before purchasing a water softener for your home, get the facts on Denver’s water hardness, or lack thereof.

The South Platte River is part of Denver Water's southern collection system and provides moderately hard water.

On the surface, it’s an easy sell.

If you don’t like spots on cleaned dishes, have challenges rinsing off soap in the bath and live in an area with “hard water” — get a water softener.

But, while Colorado may be considered by some as a state that has hard water (according to this U.S. Geological Survey map), for Denver Water customers, the surface is the very reason they should rethink buying into this pitch to soften the water in their home.

That’s because Denver’s water comes from snowmelt and is fed by mountain rivers and streams, also known as surface water. The USGS Water Science School explains that it’s actually the water systems relying on groundwater that have greater water hardness issues since small amounts of naturally occurring minerals dissolve into the water as it moves through the soil and rock.

“The hardness of our water varies during the year,” said Steve Price, water treatment engineer for Denver Water. “Denver’s water is slightly harder in the winter when our waterways and reservoirs freeze, allowing the water to absorb more minerals. It’s softer during late spring through fall when the runoff filters out some of the minerals as the water makes its way into our reservoirs.”

The USGS classifies soft water as anything under 60 milligrams per liter of calcium carbonate. Hard water is identified in the range of 121 to 180 mg/L. There are no health concerns associated with calcium carbonate levels, but hard water can be a household nuisance and leave a chalky or mineral aftertaste.

Denver Water uses two main collection systems for its supply. The southern collection system, which is considered moderately hard with a range of 75 to 120 mg/L, and the softer northern collection system where calcium carbonate levels are typically between 40 and 50 mg/L.

Denver's water is considered to be soft to moderately hard.

“We’re fortunate to have such a pristine water source here in Denver, as our goal is to not only provide safe and reliable drinking water supply, but also one that tastes, smells and looks good,” said Price.

Some people may still choose to invest in a water softener for their home, but Price emphasizes the importance of properly maintaining any in-home device that impacts drinking water.

“Once the water goes through a supplemental water treatment device, we can no longer ensure that it meets Denver Water’s high-quality standards,” he said. “It’s vital that customers properly maintain their water softeners so that they are not unknowingly affecting the safety of their drinking water.”

Despite Denver’s soft to moderately hard water supply, it’s not uncommon to see a sales force for water softening systems in the community.

But buyer beware. In-home water treatment devices have actually been used in elaborate and expensive scams, like the Greeley Tribune exposed earlier this year in its story, “Habitat for Humanity director vows action in wake of ‘misleading’ tactics used to sell Habitat homeowners soft water systems.”

“The bottom line is that when it comes to the safety and integrity of your drinking water, make sure you have all the facts,” Price said. “Contact your utility, research the quality of your water supply and thoroughly investigate any in-home treatment device, water softener or otherwise, before making a purchase.”


Denver Water provides detailed information about water quality from the source to the tap, including annual water quality reports detailing monitoring programs and results, here.