What is a water softener?

What does a water softener do?

It trades minerals: as water flows through the resin, calcium and magnesium stick to the beads and sodium or potassium goes into the water in their place, and the salty rinse that later cleans the beads goes down the drain. The Minnesota Department of Health and Penn State Extension describe the exchange: “Resin beads inside the softener trap the calcium and magnesium and exchange them for sodium or potassium.” Source: Minnesota Department of Health, read 2026-10-29. “The water flows through the unit while the resin releases its sodium ions and readily trades them for the calcium and magnesium ions.” Source: Penn State Extension, read 2026-10-29. “The water flowing out of the device is now considered soft.” Source: Penn State Extension, read 2026-10-29. “After passing through the beads, the resulting chloride solution becomes a waste stream that goes down the drain and ultimately into the environment.” Source: Minnesota Department of Health, read 2026-10-29.

How do Minnesota and Penn State describe a water softener?

A water softener is a tank of resin beads plumbed into the home water line that takes out the calcium and magnesium that make water hard, so the water leaving it is soft. The Minnesota Department of Health and Penn State Extension both call it an ion exchange unit: “Home water softeners, also called ion exchange units, are appliances that remove calcium, magnesium, and other minerals from drinking water.” Source: Minnesota Department of Health, read 2026-10-29. “A water softener, also called an ion exchange unit, will effectively accomplish the latter option.” Source: Penn State Extension, read 2026-10-29. “Soft water contains lower levels of calcium and/or magnesium than hard water.” Source: Minnesota Department of Health, read 2026-10-29.

How often does a water softener regenerate?

It depends on the control and the size: timed models regenerate on a set schedule, demand-control models after a set number of gallons, and the University of Minnesota Water Resources Center says a softener should be sized to run three to five days between regenerations. Penn State Extension estimates about 50 gallons of water for each cycle: “Timed models have programmable timeclocks that will regenerate on a predetermined schedule and then return to service.” Source: Penn State Extension, read 2026-10-29. “Demand-control models, with either electrical and mechanical sensors, usually regenerate after so many gallons of water have been softened.” Source: Penn State Extension, read 2026-10-29. “Water softeners should be sized to work three to five days without regeneration and designed to treat water without significant pressure loss.” Source: University of Minnesota Water Resources Center, read 2026-10-29. “A water softener that is too small will run out of soft water and need to regenerate more frequently.” Source: University of Minnesota Water Resources Center, read 2026-10-29. “Estimates indicate that about 50 gallons of water are used for each regeneration cycle.” Source: Penn State Extension, read 2026-10-29.

Is softened water safe to drink?

The sources treat added sodium as the main drinking-water question: Penn State Extension puts it at 7.5 milligrams per quart for each grain per gallon of hardness removed, and the EPA guidance level of 20 mg/L was set for people limited to 500 mg of sodium a day. The Minnesota Department of Health suggests an unsoftened tap for drinking: “A water softener that uses sodium chloride (salt) increases the amount of sodium in the water you drink at home.” Source: Minnesota Department of Health, read 2026-10-29. “The exchange of hardness minerals for sodium adds 7.5 milligrams per quart for each gpg of hardness removed.” Source: Penn State Extension, read 2026-10-29. “At the present time the EPA guidance level for sodium in drinking water is 20 mg/L.” Source: U.S. Environmental Protection Agency (EPA), Office of Water, read 2026-10-29. “Domestic water softeners can increase sodium levels to more than 300 mg/L in drinking water (NAS 1977).” Source: U.S. Environmental Protection Agency (EPA), Office of Water, read 2026-10-29. “If you or someone in your home has a history of high blood pressure, consult a doctor about drinking softened water.” Source: Minnesota Department of Health, read 2026-10-29. “Have an un-softened tap for cooking and drinking.” Source: Minnesota Department of Health, read 2026-10-29.

Does a water softener purify water?

No: a softener removes hardness minerals, and Penn State Extension says softening is often mistaken for purifying. Some softeners also take out some iron, up to about 3 mg per liter according to the University of Minnesota Water Resources Center, but a softener does not necessarily remove the more serious contamination problems. The sources say: “As the water treatment industry has grown in the U.S., the concept of water softening has often been misconstrued as a purifying, cleansing or conditioning process.” Source: Penn State Extension, read 2026-10-29. “But the reality is that water softening simply removes hardness minerals and eliminates problems that are a nuisance and not a threat to human health.” Source: Penn State Extension, read 2026-10-29. “It is also important to note that water softeners will not necessarily remove any of the more serious drinking water contamination problems.” Source: Penn State Extension, read 2026-10-29. “Depending on your water quality, some softeners may be able to fully or partially remove copper, iron, manganese, and radium, in addition to calcium and magnesium.” Source: Minnesota Department of Health, read 2026-10-29. “In general, water softeners may remove up to 3 mg per liter of iron in the water.” Source: University of Minnesota Water Resources Center, read 2026-10-29.

What is water softener salt made of?

Softener salt is either sodium chloride or potassium chloride, added to the brine tank to make the rinse that recharges the resin; the University of Minnesota Water Resources Center says sodium chloride is the most common and every softener salt product contains chloride. The Minnesota Department of Health names potassium chloride as the lower-sodium choice: “Regardless of labelling, all softener salt products contain chloride.” Source: University of Minnesota Water Resources Center, read 2026-10-29. “While there are many salt products available, the base of these products is either sodium chloride or potassium chloride.” Source: University of Minnesota Water Resources Center, read 2026-10-29. “Sodium chloride is the most commonly used salt in water softener brine tanks.” Source: University of Minnesota Water Resources Center, read 2026-10-29. “Potassium chloride is used when there are health concerns with sodium intake.” Source: University of Minnesota Water Resources Center, read 2026-10-29. “Regenerate your softener with potassium chloride instead of sodium chloride (salt).” Source: Minnesota Department of Health, read 2026-10-29.

What does grains per gallon mean for a water softener?

Grains per gallon (gpg) is the unit softeners and water tests use for hardness: one grain per gallon equals about 17 mg/L of calcium carbonate, so 7 gpg is roughly 120 mg/L, the top of the band the U.S. Geological Survey calls moderately hard. The softener is then set to the hardness of the water it treats: “A second expression of hardness is grains per gallon (gpg) of calcium carbonate.” Source: Penn State Extension, read 2026-10-29. “A gpg is used exclusively as a hardness unit and equals approximately 17 mg/l or ppm.” Source: Penn State Extension, read 2026-10-29. “General guidelines for classification of waters are: 0 to 60 mg/L (milligrams per liter) as calcium carbonate is classified 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.” Source: U.S. Geological Survey (USGS) Water Science School, read 2026-10-29. “Make sure the softener is set to the hardness of your water supply.” Source: Minnesota Department of Health, read 2026-10-29.

Do I need a water softener?

Nothing requires one: the Minnesota Department of Health says hardness above 7 grains per gallon (120 mg/L) is where a softener may be needed, and the University of Minnesota Water Resources Center says 5 to 7 gpg may be acceptable to many homeowners. Water that a utility already softens needs no second softener: “There is no requirement to soften your water.” Source: Minnesota Department of Health, read 2026-10-29. “If your water’s hardness is greater than 7 grains per gallon or 120 mg/L, then you might need a water softener to ensure your appliances run well and to improve the taste, smell, or look of your water.” Source: Minnesota Department of Health, read 2026-10-29. “Hardness less than 5 - 7 grains per gallon (gpg) may be acceptable to many homeowners.” Source: University of Minnesota Water Resources Center, read 2026-10-29. “The decision "to soften or not to soften" is a matter of personal preference not necessity.” Source: Penn State Extension, read 2026-10-29. “Soft water provided by a utility does not need additional softening and may cause corrosion issues for your home.” Source: Minnesota Department of Health, read 2026-10-29.

Sources

• Home Water Softening: Frequently Asked Questions — Minnesota Department of Health; published 2022-10-03; read 2026-10-29.
• Water Softening — Penn State Extension; published 2025-09-08; read 2026-10-29.
• Hardness of Water — U.S. Geological Survey (USGS) Water Science School; published 2026-08-24; read 2026-10-29.
• Residential softening — University of Minnesota Water Resources Center; read 2026-10-29.
• Drinking Water Advisory: Consumer Acceptability Advice and Health Effects Analysis on Sodium (EPA 822-R-03-006) — U.S. Environmental Protection Agency (EPA), Office of Water; published 2003-02; read 2026-10-29.