Answers to common questions we receive about salt use and chloride
Review these chloride FAQs and helpful tips on salt reduction strategies. Topics covered in the list of chloride FAQs include the science of chloride, hard water, water softeners, and road and sidewalk salt application.
What is chloride?
Chloride is an ion (charged particle) that is most commonly found in sodium chloride, also known as table salt or rock salt. When salt dissolves in water, it separates into sodium ions and chloride ions. Chloride can also be found in other compounds, like magnesium chloride and potassium chloride.
Why is chloride a concern?
High concentrations of chloride are harmful to freshwater plants and animals. It takes only one teaspoon of salt to bring five gallons of freshwater to the chloride level that starts to affect freshwater life, according to the U.S. Environmental Protection Agency. Chloride can also interfere with healthy ecosystem processes and kill vegetation, which is why you might see dead grass next to sidewalks where road salt was applied in the winter.
Where does chloride come from?
Most chloride that ends up in the District’s sewer system comes from water softeners used in residential, commercial and industrial buildings. Some industries also use salt water in their processes and discharge chloride to the sewer. The sanitary sewer also receives chloride from road salt, but most road salt ends up in lakes, streams and drinking water. Small amounts of chloride come from soaps, detergents, other cleaning products and food waste.
How does chloride get into the environment?
Chloride from water softeners and other household and industrial sources is flushed into the sewer and then travels to the wastewater treatment plant. Treatment plants are designed to remove solid particles, like grit and sand, and to biologically degrade organic waste, such as food and human waste. Once chloride is dissolved in water, it cannot be removed by standard treatment processes. Chloride that comes to the Nine Springs Treatment Plant passes through the plant to Badfish Creek or Badger Mill Creek, and eventually to the Rock, Sugar and Mississippi rivers. About 100 tons of salt pass through the plant to the environment each day. This is equal to the amount of road salt loaded into 20 five-ton salt trucks. For information about the impact of road salt on the environment, visit the Wisconsin Salt Wise website.
Chloride FAQs: Hard water
What makes hard water hard?
Rainwater that falls is “soft,” meaning it does not contain any minerals. As it percolates through the soil and rock toward aquifers and wells, rainwater dissolves any minerals present, which can include calcium and magnesium. Water with substantial amounts of calcium and magnesium is referred to as “hard water.”
How do you measure hardness?
Hardness is measured in terms of grains per gallon (g/gal) or milligrams per liter (mg/L). If you were to evaporate one gallon of water with a hardness of 5 g/gal, the residue would be equal to one 5-grain aspirin tablet. Laboratories often record hardness as mg/L or parts per million (ppm). One g/gal of hardness is equal to 17.1 mg/L of hardness. In the example above, 5 g/gal equals 85.5 mg/L hardness. Water that is 10 g/gal or more is considered very hard.
Why is my water hard?
Most drinking water in Dane County comes from groundwater held in an aquifer far below the surface. The wells that supply water for the Madison Water Utility range from 744 feet deep to 1,175 feet deep. Dolomite is composed of calcium magnesium carbonate and is the source of the minerals that make our water hard. The hardness of water from the Madison Water Utility is typically 16 to 24 g/gal.
You can look up the average water hardness for your address on our water hardness map.
What is the problem with hard water?
The minerals in hard water can be deposited as scale on pipes and in hot water heaters. They also chemically interact with soaps and detergents and make them less efficient. For example, it takes 50% to 75% less detergent to clean laundry in soft water than in hard water.
Chloride FAQs: Water softeners
How is water softened?
Home water softeners have two tanks: a mineral tank that contains a resin in the form of small beads, and a brine tank that holds the sodium chloride (salt) solution. As water flows through the mineral tank, the hard minerals, magnesium and calcium ions, replace sodium ions on the resin. This process is called ion exchange. The water that flows out is considered “soft” because sodium ions do not build up on pipes as lime or interfere with detergents and soaps.
What is water softener regeneration, and what does it mean for salt use
Eventually, the resin reaches its limit as to how much calcium and magnesium it can hold. At this point, the resin is flushed with a strong brine solution from the brine tank. Because of its high salt concentration, the brine washes off the calcium and magnesium and replaces them with sodium. The minerals and brine wash go down the drain and into the sewer system. New salt must be added regularly to the brine tank to replace the salt that is used to regenerate the resin.
The regeneration cycle can be initiated by a timer or by demand. A timer-regulated softener regenerates the resin after a fixed amount of time regardless of how much water is used. A demand-initiated regeneration (DIR) softener either tracks the amount of water used or utilizes a hardness sensor to indicate the resin is near capacity and needs to be regenerated. A DIR softener is the more efficient softener in terms of salt and water usage.
Is potassium chloride a better choice than sodium chloride for my water softener?
No. Although it consists of potassium instead of sodium, it still contains chloride. There is no advantage to using potassium chloride as your softener salt here in the Madison area. In some of the drier parts of the western United States, crops are regularly irrigated with treated wastewater. Certain crops are sensitive to sodium, and in those areas, they are promoting the use of potassium chloride over sodium chloride.
What about water softeners in seasonally occupied homes?
For buildings that are only occupied for part of the year, like summer cabins or cottages, make sure to unplug the softener when you leave for the season. This will prevent it from regenerating while you are away. When you return, plug it back in and reset the time of day. If any questions come up, call a professional; they can often provide assistance by phone.
Chloride FAQs: Road, parking lot and sidewalk salt
How much salt comes from road de-icing?
Road salt used to de-ice streets and highways is also a significant source of chloride to the environment. Most road salt is applied as pellets or as a sand/salt mixture. We need everyone’s help to reduce the amount of de-icing salt used. All the salt that is applied to sidewalks, driveways, roads and parking lots makes its way to our local waterways.
How much salt comes from parking lot or sidewalk de-icing?
Some estimates show that the quantity of salt used on local roads accounts for one-half of the total road salt used in Dane County. The remaining sources are sidewalks, driveways and parking lots. Using more salt than is needed has serious consequences for our waterways. Find salting best practices and success stories on the Wisconsin Salt Wise website.
Can’t I just use sand instead of salt on my sidewalk or driveway?
Unlike salt, sand does not melt ice and isn’t a direct substitute for salt. Sand’s function in the winter is to provide traction on top of slippery surfaces. Because road salt doesn’t work well below 15 degrees Fahrenheit, sand can be used when it’s very cold to help reduce the risk of slipping. It’s also important to remember that salt alternatives like sand and beet juice also have environmental impacts, so no matter what substance is used on surfaces in the winter, it’s important to use the right amount.