What Is a Water Softener?
USGS defines water hardness as the amount of dissolved calcium and magnesium in water, and classifies water with 0 to 60 mg/L of hardness as calcium carbonate as soft, 61 to 120 mg/L as moderately hard, 121 to 180 mg/L as hard, and more than 180 mg/L as very hard. It says hardness is not a health concern but can be a nuisance, causing mineral buildup in plumbing, fixtures and water heaters and poor performance of soaps and detergents.
University of Nebraska-Lincoln Extension says household water softeners are ion exchange devices that remove the hardness ions calcium and magnesium and replace them with non-hardness ions, typically sodium supplied by dissolved sodium chloride salt, or brine. It says softening adds sodium at about 8 mg/L for each grain per gallon of hardness, so water that had 10 grains per gallon of hardness ends up with about 80 mg/L of sodium. North Dakota State University Extension says potassium chloride may be substituted when health or environmental reasons call for restricting sodium, but that it is more expensive and reduces exchange efficiency on the resin.
The salt goes somewhere. The Minnesota Pollution Control Agency says many water softeners use more salt than they need, and because wastewater treatment plants cannot remove chloride, it ends up in lakes and rivers and even in drinking water. In California, Health and Safety Code section 116786 lets a local agency, by ordinance and only after making required findings, limit or prohibit residential water softeners that discharge to the community sewer system, but any such ordinance must be prospective and may not require removing softeners installed before it took effect.
Sources checked September 15, 2026. Every point below links the page it came from.
The sources behind this answer
- Medical referenceUSGS defines water hardness as the amount of dissolved calcium and magnesium in water. US Geological Survey ↗
- Medical referenceUSGS classifies water with 0 to 60 mg/L of hardness as calcium carbonate as soft, 61 to 120 as moderately hard, 121 to 180 as hard, and over 180 as very hard. US Geological Survey ↗
- Government sourceUSGS says water hardness is not a health concern but can be a nuisance, causing mineral buildup in plumbing, fixtures and water heaters and poor soap performance. US Geological Survey ↗
- Medical referenceUniversity of Nebraska-Lincoln Extension says household water softeners are ion exchange devices that replace calcium and magnesium with other ions, typically sodium from salt brine. University of Nebraska-Lincoln Extension ↗
- Medical referenceUniversity of Nebraska-Lincoln Extension says softening adds about 8 mg/L of sodium per grain per gallon of hardness, so 10 grains per gallon water ends up with about 80 mg/L. University of Nebraska-Lincoln Extension ↗
- Medical referenceNorth Dakota State University Extension says potassium chloride may replace sodium chloride when sodium must be restricted, but costs more and reduces exchange efficiency. North Dakota State University Extension ↗
- Government sourceThe Minnesota Pollution Control Agency says many water softeners use more salt than needed, and chloride that treatment plants cannot remove ends up in lakes, rivers and drinking water. Minnesota Pollution Control Agency ↗
- Regulatory filingCalifornia Health and Safety Code section 116786 lets a local agency, after required findings, limit or prohibit installing residential water softeners that discharge to the sewer. California Legislature ↗
- Regulatory filingCalifornia Health and Safety Code section 116786 says a local softener ordinance must be prospective and may not require removal of softeners installed before it took effect. California Legislature ↗
Sources checked September 15, 2026. A brand statement is the company’s own claim, which we report but have not verified. Our grades are model-based estimates, not lab tests.