Sioux Falls hard water guide (2026)

Updated October 29, 2026. General information, not legal or engineering advice. Water systems change their treatment and publish new numbers every year; check the latest report.

Quick reference

Supply	Hardness and softener setting	Source
City of Sioux Falls	250 ppm total hardness; softener setting 15 grains (2025). 270 ppm and 16 grains in 2024	City of Sioux Falls annual water reports
Lewis and Clark	168 ppm; softener setting 10 grains (2025)	City of Sioux Falls 2025 report
Sodium	Sioux Falls 34 ppm; Lewis and Clark 82 ppm	City of Sioux Falls 2025 report
Harrisburg	Buys 100% of its water from Lewis and Clark	City of Harrisburg 2025 report
Brandon	City wells; RO softening on part of the flow, about 24 grains down to about 12	AE2S; Water Conditioning and Purification (2025)
Minnehaha Community Water	Local wells plus 34% from Lewis and Clark	MCWC 2025 report
Private wells	Not federally regulated; owner responsible	U.S. EPA
Who can install	SD Plumbing Commission water conditioning contractor and installer licenses	SD Department of Labor and Regulation

How hard is Sioux Falls water?

The City of Sioux Falls 2025 annual water report lists total hardness of 250 ppm as calcium carbonate, 133 ppm from calcium and 117 ppm from magnesium, and gives a water softener setting of 15 grains per gallon. The 2024 report listed 270 ppm and 16 grains. Hardness at that level leaves scale on fixtures and in water heaters, so most Sioux Falls homes use a softener even though the city's plant already does some softening.

Where does the city's water come from?

Sioux Falls draws groundwater from the Big Sioux Aquifer and the Middle Skunk Creek Aquifer, treats water from the Big Sioux River when needed, and buys water from the Lewis and Clark Regional Water System. In a 2021 Dakota News Now tour of the Water Purification Plant, staff described tanks that soften the water by 50 percent before it's filtered, fluoridated and chlorinated. The plant was treating about 38 million gallons on a hot summer day, 17 to 18 million gallons a day in winter, and about 8 billion gallons the previous year. The city also adjusts the pH of treated water to minimize lead and copper.

Lewis and Clark water

Lewis and Clark pumps from eleven wells in an aquifer recharged by the Missouri River near Vermillion. The Minnesota Department of Health describes its treatment: lime softening that cuts total hardness from about 300 ppm to about 160 ppm, carbon dioxide to adjust pH, sand and anthracite filters that remove iron and manganese, then disinfection and fluoride. First water was delivered in July 2012, and Tea serves as the system's hub. The Sioux Falls report lists Lewis and Clark water at 168 ppm hardness, a 10-grain softener setting and 82 ppm sodium. Harrisburg buys all of its water from Lewis and Clark.

Brandon's new treatment

Brandon produces groundwater from its own wells. AE2S, the engineer on the plant expansion, describes doubling capacity with a 2,000 gallon-per-minute addition that uses reverse osmosis softening on half the water to reduce hardness by 50 percent, along with aeration for iron removal and filtration for radium removal. A 2025 Water Conditioning and Purification article put the change at roughly 24 grains down to 12. If your softener was set before the change, have it retested and reprogrammed.

Rural water and private wells

Minnehaha Community Water Corp serves more than 13,435 customers with groundwater from local wells and buys 34 percent of its water from Lewis and Clark, according to its 2025 report. Private wells have no annual report at all. The U.S. EPA says private well water isn't regulated by the federal government and that owners are responsible for its safety. Test for hardness, iron, manganese, nitrate and bacteria before choosing equipment.

Setting your softener

• Use the hardness for your actual supply: 15 grains for Sioux Falls city water and 10 for Lewis and Clark, per the 2025 report, or your own test.
• Add iron compensation only if a test shows iron.
• Use demand-based regeneration if your control supports it.
• Retest when your water system announces a treatment change.

Who can install a softener in South Dakota?

The South Dakota Plumbing Commission, part of the Department of Labor and Regulation, issues water conditioning contractor and water conditioning installer licenses. Per the commission, the installer license calls for two years working as a water conditioning apprentice, and the contractor license for one year as an installer. Ask a company which license it holds, and ask your city whether a plumbing permit is needed for the work.

What does it cost?

We haven't found a reliable public source for typical Sioux Falls prices, so we don't publish ranges. Cost depends on capacity, valve type, pre-filters for wells, plumbing changes and add-ons like RO. Get the model, setting, capacity and warranty in writing.

Questions to ask

• Which water supply do I have, and what hardness did you measure?
• What will you set the softener to?
• Which South Dakota license do you hold?
• Will outdoor spigots bypass the softener?
• For wells: what did the iron and sulfur results show?

Sources

• City of Sioux Falls: Annual water report (2025 data)
• City of Sioux Falls: Annual water report (2024 data)
• City of Sioux Falls: Drinking water FAQs
• Dakota News Now: Inside the Sioux Falls water treatment plant (2021)
• Minnesota Department of Health: Lewis and Clark Regional Water System
• City of Harrisburg: 2025 drinking water report (SD DANR)
• Minnehaha Community Water Corp: 2025 drinking water report (SD DANR)
• City of Brandon: 2024 Drinking Water Report
• AE2S: Brandon, South Dakota water treatment plant expansion
• Water Conditioning and Purification: A tale of water in two cities (2025)
• South Dakota Plumbing Commission: Licensing
• U.S. EPA: Private drinking water wells
• Wikipedia: Sioux Falls, South Dakota
• Wikipedia: Brandon, South Dakota
• Wikipedia: Harrisburg, South Dakota