Educational Materials on Testing Recommendations for Private Wells and Semipublic Wells                   Updated: September 2022

Testing your private well or semipublic well water provides you with information on the quality of your water and is the best way to ensure that your water supply is safe for use. It can also determine if nuisance contaminants, such as iron and manganese are present and at what levels. The following information is meant to assist owners of private wells or semipublic wells to decide what to test for and how often. These are general guidelines for private well water testing, which is not all inclusive. 

Regular testing is important because water quality can change, and, routine testing establishes a record of water quality that may help identify and solve future problems. Owners with private wells and semipublic wells are responsible for the quality of their water and are generally not required to test. However, testing is a good idea even if you do not suspect a problem because it's the only way to be sure your water is safe to drink. It is highly recommended to test water quality when buying a home so that you can make informed decisions about your purchase. A good time of year to test is after a heavy period of rain, generally in the spring or fall. 

What to Test For? How Frequently to Test?

Table 1 lists the tests recommended for all private wells even if you do not notice any problems with your water. Table 3 lists water quality issues you might encounter and what tests you should perform if you have a particular issue. Whenever you notice a change in the taste, color, odor, or clarity of your water, contact your Local Health Department or the Connecticut Department of Public Health (CT DPH), Private Well Program for assistance. 

Table 1. Recommended Tests for All Private Wells

Test(s)  When?  Why? 
Basic Indicators (see Table 2 below) Every Year 
Also any time there is repair work to the well, pump or water pipes, or if your well head was flooded. 
Provides a general indication of water quality. Required for all new wells. Some basic indicators above their acceptable limit are associated with health concerns. 
Lead (2 samples; first draw & flushed samples should be collected when testing for lead) At Least Once 
Also when planning a pregnancy or have a child under the age of 6 in the home; or, if your water is considered corrosive, test every 3-5 years.
Lead can leach from your home’s plumbing (pipes, faucets, valves, etc.) system. Corrosive water leaches lead more readily. Lead above the acceptable limit is associated with health concerns. Young children are especially susceptible to harmful effects from lead exposure. 
Arsenic, Uranium, Radon At Least Once 
Ideally, repeat test every 5 years
Arsenic, uranium and radon are naturally occurring in groundwater in some areas of CT and are associated with health concerns above their acceptable limit. Private wells with high levels have been found sporadically around CT, and levels may fluctuate.
Volatile Organic Compounds (VOCs) At Least Once
More often if a problem is identified or suspected
Gasoline, oil, solvents or industrial chemicals spilled or leaked on the ground could get into your well water. VOCs above their acceptable limit are associated with health concerns. 
 Fluoride Every 5 years when a child under 12 is present 
Fluoride can occur naturally in wells throughout CT. A child’s permanent teeth can become discolored from excess fluoride. Too little fluoride can increase risk of tooth decay. Your child’s dentist may advise you about the fluoride level in your well water. 

Table 2. Basic Indicators Test

Parameter Applicable Drinking Water Standard*  Drinking Water Standards 
 Total Coliform Bacteria  None Present 

CT DPH Action Levels

US EPA Maximum Contaminant Levels (MCLs)

US EPA Secondary MCLs (SMCLs)

*Drinking water standards may be based on aesthetics

or on associated health risk. If your water exceeds a

drinking water standard, contact your Local Health

Department or the CT DPH, Private Well Program

for assistance. For more information on drinking

water standards refer to the links above.

 Nitrate 10 milligrams/liter (mg/L) 
 Nitrite  1 mg/L 
 Sodium  100 mg/L 
 Chloride  250 mg/L 
 Iron  0.3 mg/L 

 0.05 mg/L (Based on Aesthetics)

 0.3 mg/L (Based on Health Concerns)

 Hardness  Range:  0-60= Soft;  61-120= Mod Hard; 
 121-180= Hard;  >181= Very Hard 
 Turbidity  Less than 5 standard units (SU) 
 pH  6.5 - 8.5 SU
 Sulfate  250 mg/L 
 Apparent Color  Less than 15 SU 
 Odor  Less than 2 

Table 3. Private Well Water Quality Issues and Recommended Associated Test (Troubleshooting)

 Water Quality Issue Possible Cause(s)  Recommended Water Test(s) 
 Low pH (less than 6.5) Generally naturally occurring Hardness, Alkalinity, Sulfate, Lead, Copper, Cadmium, Zinc 
Buildup of limescale (off-white chalky solids) on hot water plumbing, fixtures, kettles, etc. Reduced soap lathering.  Hardness is caused by the amount of dissolved mineral content in water, generally made up of calcium and magnesium. Hardness 
Blue or greenish stains on plumbing, fixtures or laundry. Plumbing leaks and pin hole leaks. Corrosive water (may be influenced by: pH, hardness level, alkalinity, chloride level, dissimilar metals in plumbing, etc.) pH, Hardness, Alkalinity, Sulfate, Chloride, Sodium, Lead, Copper, Cadmium, Zinc 
Rust-colored water, rust stains on clothing and plumbing fixtures, rust coating in toilet tank, foul odor
Iron, Manganese, Iron Bacteria
Iron, Manganese, Iron Bacteria
Yellow, brown or blackish stains on plumbing fixtures, yellow or brown staining to laundry
Manganese, Iron/Manganese Bacteria, Sulfur Bacteria
Manganese, Iron, Iron/Manganese Bacteria
Rotten egg odor, musty or swampy odor, tarnished copper and silverware
Hydrogen sulfide gas, high sulfates, sulfur bacteria, iron/manganese bacteria
Odor, Hydrogen Sulfide, Sulfate, Iron Bacteria, Iron, Manganese, Sulfur Bacteria, Coliform Bacteria
Cloudy, Turbid, Muddy Water
Silt, Sediment, microorganisms
Turbidity, Coliform Bacteria, Check Well Construction with an expert 
Chemical, fuel or fruity odor
Leaking underground fuel tank, gas   station fuel spill, industrial chemical spill, road runoff 
Volatile Organic Compounds (VOCs) 
Nitrates exceed 10 mg/L Nitrites exceed 1 mg/L 
Fertilizer runoff, malfunctioning septic system 
Pesticides* (refer to note below regarding testing for pesticides), Coliform Bacteria 
Radon in air exceeds 4 pCi/L, or, Uranium in water exceeds 30 ug/L
Naturally-occurring uranium in bedrock
Uranium, Radium, Radon
Recurrent gastrointestinal illness
Human or animal waste contaminating well, cracked well casing, flooded well, malfunctioning septic system
Coliform Bacteria, Nitrates, Nitrites
Bitter, metallic taste
Corrosive (low pH) water
pH, Lead, Copper
Salty, brackish taste
Road salt runoff, nearby salt storage, well near salt water, improper setting on water softener 
Chloride, Sodium, Total Dissolved Solids 
Well within 1/4 mile of current or former orchard or farmland 
Agricultural and/or arsenic-based pesticides get into well 
Nitrates, Arsenic, Pesticides* (ask for EPA Method 505)
Well within 1/4 mile of commercial or industrial area 
Gasoline, oil, solvents leaked or spilled on the ground get into well 
Volatile Organic Compounds (VOCs) 
Well flooding, ponding around well
Heavy rains, poor drainage around well
Coliform Bacteria, Basic Indicators
House foundation treated for termites before 1990
Termite pesticides can leach into well water
Pesticides* dieldrin and chlordane
Noticeable change in taste, color, odor, or clarity of your water. 
Unknown Contact your local health department or CT DPH Private Well Program

*Contact your Local Health Department, CT Dept. of Energy and Environmental Protection, or CT DPH Private Well Program for advice regarding whether you should additionally test for pesticides.

Private Water Supplies

In accordance with Section 19-13-B101 of the Public Health Code, testing is required for new wells. However, the required tests do not cover all contaminants. Water tests done during home purchases are usually required by the bank providing the mortgage. Contrary to common belief, such tests are not required by law and do not necessarily cover all contaminants.

Because this publication provides general guidelines that are not all inclusive it may be recommended to check with your Local Health Department to find out whether there are water quality problems specific to your area. It is also a good idea to ask your neighbors whether they have had water quality problems. The Connecticut Department of Public Health (DPH) Private Well Program is another resource for questions about private well testing. DPH’s Environmental and Occupational Health Assessment Program is a resource for questions about safe limits of chemicals in water and health concerns. Contact information is provided at the end of this document.

What If I Already Have A Treatment System In My Home?

If you have water treatment equipment in your home, you should monitor whether the treatment system is doing its job by testing for the specific contaminant(s) that the system is treating for. Be aware that water treatment systems are designed for specific contaminants and will not necessarily remove all contaminants. Periodically test your water quality before and after treatment to be sure the system is continuing to work properly and to monitor any fluctuation in your raw water quality. Refer to Publication #19: Questions to Ask When Purchasing Water Treatment Equipment for Your Home for more information about treatment.

How Do I Get My Water Tested?

You can have your water tested at any State-certified water testing lab. A current list of certified labs can be obtained from the DPH Certified Environmental Labs website. Make sure the private lab is certified to test drinking water for the contaminants you are requesting. In most cases, you can collect a sample of your tap water yourself, although some labs may send a technician to collect a sample at your request. If you collect your own sample, carefully follow the laboratory's instructions to obtain a good sample. How to take a sample varies depending on the tests being performed. For example, some contaminants such as lead and copper may require that water remain stagnant in the pipes for a minimum of 6 hours and be collected upon the first draw of water. Other contaminants require that the water be flushed or run for a minimum period of time before collecting the sample. Some contaminants require special sample bottles and procedures. Cleanliness is a must; make sure that nothing but the water comes in contact with the opening of the bottle or the inside of the cap. Timeliness is important, too. Some contaminants deteriorate or change form with time. Most water samples need to be kept cool when being taken to the lab. To assure accurate results, after collecting your water samples make certain the lab receives them within the specified time directed on the instructions.

Keep Records

Keep a record of all your water test results with dates. A change in the concentration of a contaminant may indicate that a water quality problem is developing. Additionally, by comparing test results over time, you may find that a change in treatment is necessary or that a treatment device is not functioning properly. 

Understanding Your Water Test Results

There are federal and state criteria for many of the substances that you might find in your private well water. These criteria indicate the concentrations above which your water might not be safe to consume or use, or, might have an aesthetic affect on your water such as imparting a taste, odor or color.

DPH sets state drinking water criteria specifically for private wells, called Action Levels. Action levels are developed to protect you from health risks. Federal drinking water criteria to protect your health are set by the US Environmental Protection Agency (EPA) and are called Maximum Contaminant Levels (MCLs). You should compare the results of your private well tests to these criteria to determine whether the water is safe. If any of your water quality test results are higher than an Action Level or an MCL, you should: 

  • Retest the water to confirm the exceedance
  • Stop drinking the water until the issue is resolved
  • Contact your Local Health Department or the CT DPH, Private Well Program for specific guidance
  • Consider installing treatment to remove the contaminant(s) from your water: refer to DPH's Private Well Water Treatment: How to Get Started and Helpful Resources for more information about treatment

Refer to CT DPH’s Chemical Contaminants in Private Wells fact sheet for more information on how drinking water criteria are set.

EPA also sets drinking water criteria to protect you from aesthetic concerns such as taste, color and odor. These criteria are called Secondary Maximum Contaminant Levels (SMCLs). Secondary contaminants themselves do not necessarily present a health risk but could be an indication that your water has problems that may pose a health risk. For example, if the pH of your water is too low it may cause your water to be corrosive. Corrosive water can leach metals like lead and copper more readily from pipes and fixtures. High levels of lead in your water does pose a health risk, particularly for young children.

Results of a Basic Indicators Test should be compared with the appropriate limits shown in Table 2 in this fact sheet. However, be aware that some of the parameters in the Basic Indicators Test are based on aesthetic concerns and some are based on health risk. If your water tests results exceed any of the limits on the Basic Indicators Test, contact your Local Health Department or the DPH, Private Well Program for advice regarding whether you should stop drinking the water. 

Protect Your Well!

You can help protect your private well water quality by paying careful attention to what you do around your well. Pay attention to nearby neighboring activities as well. Regular testing and good practices to prevent contamination can help ensure that your well supplies you and your family with good quality drinking water. Here are some important ways you can protect your drinking water well:

  • Locate new wells far from any potential contamination sources
  • Hire a professional to construct new wells or to periodically inspect existing wells
  • Use backflow prevention devices on outdoor hose bibb spigots
  • Properly seal abandoned and unused wells
  • Never flush gasoline, oils, chemicals, or solvents down the sink or toilet to a septic system
  • Inspect and properly maintain your septic system
  • Keep livestock and pet waste away from your well
  • Do not allow surface wash, especially from road, driveway or roof runoff to collect around your well
  • Do not mix or use fuels or other hazardous materials near your well
  • Do not use or over apply products used to melt snow and ice, fertilizers, pesticides and herbicides near your well
  • Do not allow waste oils or gasoline to get into soil (never perform automotive repair on exposed soils)
  • Make sure home heating tanks are above ground or in basement, and periodically check for leaking
  • Test your private well water according to the recommendations listed in this publication 
  • Refer to Private Wells: Best Management Practice Checklist for more information

For More Information

CT Department of Public Health:

Your CT Local Health Department

CT Department of Energy & Environmental Protection:

For more information regarding specific private well water contaminants, water treatment technologies and guidance, please refer to the CT DPH, Private Well Program: Publications and Fact Sheets page.