Sulfate In Well Water

Sulfate occurs naturally in most of Minnesota’s groundwater. Higher levels of sulfate are common in the western part of the state. At high levels, sulfate can give water a bitter or medicinal taste and can have laxative effects.

You can find out the level of sulfate in your water by having the water tested at a laboratory.

Health risks for humans

People who are not used to drinking water with high sulfate can get diarrhea and dehydration from drinking the water. Infants are often more sensitive to sulfate than adults. To be safe, only use water with a sulfate level lower than 500 milligrams per liter (mg/L) to make infant formula. Older children and adults may get used to high sulfate levels after a few days.

Health risks for animals

Animals are also sensitive to high levels of sulfate. In young animals, high levels may be associated with severe, chronic diarrhea and even death. Animals tend to get used to sulfate over time. Diluting water high in sulfate with water low in sulfate can help avoid problems of diarrhea and dehydration in young animals and animals not used to drinking high sulfate water. Contact a veterinarian or your county office of the Minnesota Extension Service for more information.

Other problems Sulfate can cause

Sulfate levels above 250 mg/L may make the water taste bitter or like medicine. High sulfate levels may also corrode plumbing, particularly copper piping. In areas with high sulfate levels, plumbing materials more resistant to corrosion, such as plastic pipe, are commonly used.

Ways to treat Sulfate

Four types of treatment systems will remove sulfate from drinking water:

• Reverse osmosis pushes water through a membrane with tiny pores. The membrane stops many contaminants, including sulfate, while allowing water to pass through. Reverse osmosis usually removes between 93 and 99 percent of the sulfate in drinking water, depending on the type of treatment unit.
• Distillation is a process that boils water, making steam. The steam rises and leaves contaminants, such as sulfate behind. With proper operation, distillation units can remove nearly 100 percent of sulfate.
• Anion exchange is the most common method of removing large quantities of sulfate from water for commercial, livestock, and public supplies. It is not commonly used for individual household water treatment. It is a process that replaces negatively charged ions (such as sulfate) with sodium chloride or potassium chloride (salts).
• Adsorptive media filtration has a charged media bed that can force ions of the opposite charge (such as sulfate) to be pulled out of the water and attach to the media.

Learn more about these treatment options at the Home Water Treatment webpage.

A few other things to note about home water treatment for sulfate:

• If both a water softener and a sulfate removal system are used, the water softener is usually placed before the sulfate removal system.
• Water softeners, carbon filters, and sediment filters do not remove sulfate.
• Any water treatment system requires proper operation and maintenance to ensure that it continues to function properly. It is important to follow the recommendations of the manufacturer and installer for the maintenance of the water treatment system.

How Sulfate gets into groundwater

As water moves through soil and rock formations that contain sulfate minerals, some of the sulfate dissolves into the groundwater. Minerals that contain sulfate include magnesium sulfate (Epsom salt), sodium sulfate (Glauber’s salt), and calcium sulfate (gypsum).

Sulfate in Minnesota groundwater

The level of sulfate in most groundwater in Minnesota is low, less than 250 milligrams per liter (mg/L). High levels of sulfate (sometimes above 1000 mg/L) are more common in the southwestern areas of Minnesota and along the western boundary of the state. High levels of sulfate also occur, though less commonly, in some wells in the northeastern and southeastern parts of the state.

Should I test my well water for anything besides Sulfate?

Yes. Both natural sources and human activities can contaminate well water and cause short-term or long-term health effects. Testing your well water is the only way to detect most of the common contaminants in Minnesota groundwater; you cannot taste, see, or smell most contaminants. For more information on common contaminants in private well water, please visit: Well Testing, Results, and Options.

Other contaminants sometimes occur in private water systems. You may also consider testing for:

• Volatile organic chemicals if the well is near fuel tanks or a commercial or industrial area.
• Agricultural chemicals commonly used in the area if the well is shallow and is near cropped fields or handling areas for agricultural chemicals or is in an area of geologic sensitivity (such as fractured limestone).
• Fluoride if children or teenagers drink the water.

Print information brochure

Sulfate in Well Water (PDF)

Questions

Well Management Section
651-201-4600 or 800-383-9808
health.wells@state.mn.us

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