Residential Drinking Water Wells: Water Quality (2nd in Series)

According to the South Carolina Department of Health and Environmental Control (SCDHEC), more than 20% of South Carolina residents depend on private wells for their source of residential drinking water.1 The residents using these wells are responsible for regular maintenance, testing, and treatment to ensure that the well provides safe drinking water.

Water Quality Parameters

Comprehensive water quality testing should be conducted following well installation and if results of recent testing are not available (Table 1). Additionally, annual testing is recommended for priority parameters, including bacteria, nitrates, total dissolved solids (TDS), and pH (Table 1).

Table 1. Recommended testing schedule for well water. Adapted from Texas Well Owner Network, 2019, “Well Owner’s Guide to Water Supply”.2

Frequency Action
Initial, and if recent sampling results are unavailable Comprehensive water quality testing for arsenic, chloride, copper, fluoride, hardness, iron, lead, manganese, nitrate, pH, radium, sodium, sulfate, total coliform bacteria, total dissolved solids (TDS), and uranium.
Annually Water quality testing for total coliform bacteria, nitrate, and total dissolved solids (TDS).
Monthly Visual inspection for changes in turbidity, color, odor, or taste in the water.

Federal regulations include primary and secondary drinking water standards. Primary drinking water standards include parameters such as total coliform bacteria and nitrates due to their ability to pose a potential threat to human health if found in concentrations above the Maximum Contaminant Level (MCL).3 Secondary drinking water standards address aesthetic considerations and include parameters such as pH and TDS.4 Common water quality concerns for private drinking water wells are summarized in Table 2.

Information on SCDHEC’s testing services is available at the Well Water Quality Testing Services or see HGIC 3870, Testing Drinking Water.

Table 2. Summary of common water quality concerns for private residential drinking water wells.

Parameter Standard Impacts Treatment
Primary3 Secondary4
pH 6.5 – 8.5 Pipe corrosion, altered taste/feel4 •Additional Treatment
•Acid feeder or soda ash feeder
Total Dissolved Solids (TDS) 500 mg/L Varies, depending on cause
Ex: colored water; staining; salty taste4
Varies, depending on cause
Bacteria 0 colonies /100mL of water Infection of gastrointestinal tract (nausea, vomiting, diarrhea, fever, etc.) •Boil water before use
•Retest water to confirm results
•Disinfect well
Nitrate 10 mg/L Illnesses; shortness of breath, blue-baby syndrome3 •Use alternate water source **boiling will increase levels!
•Additional filtration (e.g., ion exchange, reverse osmosis, distillation)
•Eliminate nitrate source
Radon Becomes airborne, can lead to lung cancer5
Radium 5 pCi/L Accumulates in bones, increased risk of cancer3
Arsenic 0.010 •Skin damage
•Problems with circulatory system
•Increased risk of cancer3
•Increased concern if high pH
•Additional Treatment (e.g., reverse osmosis, ion exchange, distillation)6,7
Lead 0

Action level = 0.015 mg/L

•Infants/Children: Delays in physical/mental development
•Adults: kidney problems, high blood pressure3
•Often result of corrosion of pipes3
•Additional treatment (e.g., reverse osmosis, distillation, filtration)8
Copper Action level = 1.3 mg/L •Gastrointestinal issues (short-term exposure)
•Liver/kidney damage (long-term exposure)3
•Often result of corrosion of pipes due to low pH3
•Additional treatment (e.g., reverse osmosis, distillation, ion exchange)9
Fluoride 4.0 mg/L 2.0 mg/L •Bone pain, tenderness, disease3
•tooth discoloration4
•Additional treatment (e.g., filtration, reverse osmosis, ion exchange, distillation)10


Fecal coliform bacteria are microscopic organisms found in the feces of humans and other warm-blooded animals that suggest the presence of pathogenic bacteria, viruses, and parasites that can cause illness in humans. Escherichia coli (E. coli), a type of fecal coliform bacteria, are currently considered the best indicator of potential human health risks in drinking water. There should be no E. coli in the well sample. When fecal bacteria counts are high, there is a greater chance that pathogenic organisms are also present.

What are the Primary Sources of Bacteria in Well Water?

Fecal bacteria commonly come from septic systems, livestock, pets, wildlife, and humans. Household pets, especially dogs, can be a major source of bacteria. A single gram of dog feces (the weight of a dollar bill) contains 23 million fecal coliform bacteria, so proper disposal of pet waste is essential to protecting water quality.11 Waterborne diseases such as hepatitis, cholera, and salmonella are associated with elevated bacteria levels and can pose severe risks to human health. To avoid contamination, see Table 3, which showcases recommended distances of sources to the wellhead.

For more information, see HGIC 1877, E. coli & Water Health.

Table 3. Potential contaminants and distance/direction they should be located away from drinking water wells.2

Potential Contamination Source: Minimum Distance/location from Wellhead:
Septic tank 75 ft.
Septic drain field 100 ft.
Livestock waste 150 ft.
Pet waste 150 ft.
Livestock Locate pastures down slope from well
Runoff/other contaminants Store materials and direct stormwater down slope from well


Nitrate (NO3-) can be naturally occurring from erosion of natural deposits and can also come from fertilizers and human or livestock waste runoff.5 High levels of nitrate in drinking water can be dangerous to health, especially for infants and pregnant women. Infants below the age of six months who drink water containing nitrate above the MCL of 10 mg/L could become seriously ill and, if untreated, may die. Symptoms include shortness of breath and blue-baby syndrome or Methemoglobinemia.

Be sure to test the well water for nitrate and bacteria after extreme weather events, such as flooding. Wells that are shallow, have been dug or bored, or are submerged by floodwater are particularly vulnerable to contaminants.12


The pH measurement shows how acidic or alkaline a substance is and is represented on a scale from 0 (very acidic) to 14 (very alkaline), with 7 being neutral. The secondary standard for the pH of your well or drinking water is 6.5 – 8.5. When your water has a pH outside of this range, it can cause several problems, including pipe corrosion and altered taste or feel.13

Total Dissolved Solids

Total Dissolved Solids, or TDS, refers to the level of dissolved minerals found in the water. As water moves underground or overland, it dissolves a variety of compounds, including metals, salts, and organic compounds.14 These can come from sources such as on-site sewage systems, runoff from urban, industrial, or agricultural areas, or even natural sources in groundwater like bedrock and salt deposits – any soluble mineral that encounters the water may be a source. For coastal areas in SC, saltwater intrusion may contribute to the TDS concentration. When TDS levels are elevated, you may experience deposits/stains on plumbing fixtures, a salty taste, or even observe damage to soil or plants when the water is used for irrigation.

TDS test results should be below the 500 mg/L Secondary MCL and should be relatively consistent. Changes in TDS may indicate the presence of potentially harmful drinking water contaminants, including nitrates, metals, and agricultural or industrial chemicals. Although the test shows the level of dissolved solids, it does not identify the compound(s) causing it or the source. Further testing is needed to determine the specific dissolved solids present.

Additional Parameters

Depending on your region, the life of the well, or changes in surrounding land use, there may be additional screenings that should be performed for your well. Factors affecting the frequency of testing could include where you live, sensitivities of household residents, source aquifer, or water quality concerns identified during regular screenings. Pursue additional testing if your well has a low pH or you notice a change in water appearance or TDS values.

As a good practice, the parameters noted here should be tested at initial installation and/or when vulnerable (young, elderly, pregnant) people reside in your home.


Radon is an odorless, colorless, and tasteless gas that is formed through the radioactive decay of uranium and radium.15 It can be present in the air in your home and in your well water. Although there are no EPA standards for radon in drinking water, a high level of radon in your home’s air quality is a signal to test your drinking water well. SCDHEC may provide free radon air quality test kits to SC residents; see SCDHEC’s Radon website for more information. (


Radium can be found in groundwater and is the result of the breakdown of naturally occurring radioactive material in underlying rock. Although immediate health concerns are low, long-term exposure to elevated radium concentrations in drinking water may increase a person’s risk of developing certain types of cancer. Radium in well water tends to be more common throughout the Sandhills region of SC when compared to other regions of the state.


Arsenic may be naturally present in groundwater, particularly in many SC aquifers, though it can also be influenced by industry and pesticides. Higher levels of arsenic can be, though not always, associated with higher pH. If you have a pH above the recommended range (8.5), it’s a good idea to test for arsenic if it has not been analyzed recently. Long term exposure to arsenic may contribute to an increased risk of cancer.3

Lead & Copper

In order to protect health, it is recommended that there should be no lead present in your water and ≤1.3 mg/L of copper. Given the impact of lead, especially on cognitive and physical development in children, heavy metal testing is suggested, especially if corrosion is suspected or if children, pregnant women, or anyone with a compromised immune system consumes the water. The underlying geology can occasionally be a source of lead and copper. However, most often, lead and copper are a result of corrosion of the pipes, faucets, or fixtures, which can occur when pH is lower than 6.5. If tests indicate lead or copper is present due to corroding pipes, homeowners should try to find and eliminate the source or, if that is not feasible, install a “point of use” treatment system. For additional information, see HGIC 1902, Residential Drinking Water Well: Treatment Options (ADD LINK) and Clemson University’s Lead in Drinking Water.


Fluoride is naturally occurring, possibly at high concentrations, in some of our deep groundwater aquifers. Fluoride at low levels (0.7ppm) is often added by many of our public utilities into municipal drinking water to prevent tooth decay. However, too much fluoride can be harmful. Particularly in young children, elevated concentrations of fluoride can cause fluorosis, which is the pocking and discoloration of teeth. The EPA recommends no more than 2.0 mg/L of fluoride for children under eight years old4 and 4.0 mg/L for all ages.3


For more information regarding private well screening and education in SC, see HGIC Fact Sheets: HGIC 1901, Residential Drinking Water Well: Well Components and HGIC 1903, Residential Drinking Water Well: Water Treatment Options; or visit Clemson Extension’s Be Well Informed program, which empowers residents relying on private wells to understand, maintain, and test for safety of their drinking water.

Related Information


  1. South Carolina Water Use Report 2020 Summary. Columbia (SC): SC Department of Health and Environmental Control. 2021 Aug.
  2. Texas Well Owner Network – Well Owner’s Guide to Water Supply. College Station (TX): Texas A&M University. 2019 Apr.
  3. National Primary Drinking Water Regulations. Washington (DC): US Environmental Protection Agency. [accessed 13 Jan 2023].
  4. Secondary Drinking Water Standards: Guidance for Nuisance Chemicals. Washington (DC): US Environmental Protection Agency. [accessed 13 Jan 2023].
  5. Wellcare® information about Water Treatment. Washington (DC): Water Systems Council. [accessed 2 May 2023].
  6. Treatment Technologies for Arsenic Removal. Cincinnati (OH): US Environmental Protection Agency National Risk Management Research Laboratory. 2005 Nov.
  7. Drinking Water Problems: Arsenic. College Station (TX): Texas A&M AgriLife Extension. 2020 Aug.
  8. Drinking Water Problems: Lead, Texas A&M AgriLife Extension:
  9. Drinking Water Problems: Copper. College Station (TX) Texas A&M AgriLife Extension. 2006 Jan.
  10. Fluoride in Private Drinking Water Wells. Amherst (MA): University of Massachusetts Amherst. 2007 Jun.
  11. Muncie Sanitary Stormwater Fact Sheet: Pet Waste and Water Quality. Muncie (IN): Muncie Sanitary District [accessed Jan 2023].
  12. Private Wells. Atlanta (GA): US Center for Disease Control. [accessed 13 Jan 2021].
  13. What’s In My Water? College Station (TX): Texas A&M Extension. 2003 Apr,
  14. Virginia Household Water Quality Program: Total Dissolved Solids (TDS) in Household Water. Blacksburg (VA): Virginia Cooperative Extension. 2011.
  15. Radium and Drinking Water. Columbia (SC): SC Department of Health and Environmental Control. 2010 May.

Originally published 10/23

If this document didn’t answer your questions, please contact HGIC at or 1-888-656-9988.

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