Drinking Water and Private Wells

Drinking water is one of our most valuable and vulnerable resources. In Idaho 95% of our drinking water comes from groundwater which is precipitation, surface water, and irrigation water that has been absorbed into the ground where is collects.

Contaminants in Idaho’s groundwater can come from natural sources or human activities. These contaminants may affect the safety of your drinking water, especially if you rely on a private well because private wells are not regulated.

Why It’s Important to Know What’s in Your Well Water

Do you know where your drinking water comes from or what’s in it?
About 30% of Idaho residents use private wells as their main source of drinking water. Unlike public water systems, private wells are not regularly tested or monitored. This means you may be drinking water with harmful contaminants without knowing it.

If you own a private well, you are responsible for making sure your water is safe to drink.

Contaminants in groundwater can cause health problems. These may include short-term symptoms or long-term health and developmental effects. Some contaminants occur in such small amounts that you cannot taste, see, or smell them. The only way to know what’s in your water is to test it.

When and What to Test For

Regular testing helps protect your health and your family's health. Here's how often you should test your well water:

Once a year: Test for bacteria and nitrates
Every 3 to 5 years: Test for other contaminants, including metals and chemicals

Use the Groundwater Quality Near Me map to find out what contaminants may be present in your area. This can help you decide what to test for.

If your water test results show unsafe levels of contaminants:

Contact the Environmental Health Program at the Idaho Department of Health and Welfare
- Email: EH@dhw.idaho.gov
- Phone: 1-800-445-8647
Our team can help you understand your results and recommend the best way to fix the problem.
You can also review our well water testing flow charts to better understand your next steps.

How to Take a Water Sample:

How Safe is Your Well Water?

An interactive map of ground water quality conditions for Idaho's private well owners

Is My Well Water Safe from These Contaminants?

Nitrate is a chemical commonly found in fertilizers, manure, and liquid waste from septic systems. Natural bacteria in soil can convert nitrogen into nitrate. Rain or irrigation water can then carry the nitrate through the soil into groundwater.

High levels of nitrate in drinking water can be harmful. Nitrates reduce the ability of blood to carry oxygen, which can be especially dangerous for infants and pregnant people.

Additional Resources:

How to Take a Water Sample:

What to Do if Your Nitrate Levels Are High?

If your test results show high nitrate levels, review the next steps using our nitrate sampling flow chart.

Need Help Treating Your Water?

Water Treatment Options to learn how to remove contaminants from your drinking water.

Total Coliform (TC) bacteria are commonly found in soil, surface water, on plants, and in the intestines of humans and warm-blooded animals. The presence of TC bacteria in water indicates that contamination has entered the water supply.

Most TC bacteria are not harmful, but some can cause illness.

Symptoms of exposure may include:

Upset stomach
Vomiting
Fever
Diarrhea
Children and older adults are more vulnerable to these bacteria

Additional Resources:

How to Take a Water Sample:

What to Do If Your Total Coliform Bacteria Test Is Positive?

If your test results show the presence of total coliform bacteria, review the next steps using our sampling flow chart.

Need Help Treating Your Water?

Water Treatment Options to learn how to remove contaminants from your drinking water.

Arsenic is a chemical element that occurs naturally in rocks and soil. It can dissolve into groundwater and end up in private wells.

Drinking water with arsenic may harm your health, depending on how much you consume and how sensitive you are to it. Long-term exposure to low levels of inorganic arsenic can cause serious health problems, including:

Certain types of cancer
Skin changes, such as thickening or discoloration
Blood vessel problems
High blood pressure
Heart disease
Nerve damage, including numbness or pain

Additional Resources:

How to Take a Water Sample:

What to Do If Your Arsenic Levels Are High?

If your water test shows elevated arsenic levels, review your options in our arsenic sampling flow chart.

Need Help Treating Your Water?

Water Treatment Options to learn how to remove contaminants from your drinking water.

Fluoride is a natural mineral released from rocks into the soil, water, and air. In small amounts, fluoride helps protect teeth by strengthening the outer enamel. Without enough fluoride, teeth can become weaker and more likely to develop cavities. Cavities can lead to pain, infections, tooth loss, and other health issues.

However, drinking water with too much fluoride can be harmful. High levels of fluoride may cause:

Dental fluorosis (white spots or streaks on teeth)
Skeletal fluorosis (bone and joint pain or stiffness)
Arthritis
Bone damage and osteoporosis
Muscle problems and fatigue
Chronic joint issues

Additional Resources:

How to Take a Water Sample:

What to Do If Your Fluoride Levels Are Too High or Too Low?

If your fluoride test results are outside the recommended range, check our fluoride sampling flow chart to understand your next steps.

Need Help Treating Your Water?

Visit our Water Treatment Options page to learn how to adjust fluoride and other contaminants in your drinking water.

Manganese is a naturally occurring mineral found in rocks and soil in many parts of Idaho. It can enter drinking water from natural sources.

You might suspect manganese is in your water if you notice:

Discoloration (such as brownish-red water)
Staining on plumbing fixtures or laundry
A metallic taste or unpleasant odor

Drinking water with high levels of manganese over a long period may cause health problems, including:

Memory issues
Difficulty focusing or paying attention
Problems with motor skills
Learning and behavior problems in infants (under one year old)

Additional Resources:

Manganese Informational Sheet

How to Take a Water Sample:

What to Do If Your Manganese Levels Are High?

If your water test shows elevated manganese levels, review your next steps using our manganese sampling flow chart.

Need Help Treating Your Water?

Water Treatment Options to learn how to remove contaminants from your drinking water.

Selenium is a trace mineral that your body needs in small amounts to stay healthy. However, drinking water with too much selenium can be harmful. Short-term exposure to high levels of selenium in drinking water may cause:

Nausea
Vomiting
Diarrhea

How to Take a Water Sample:

What to Do If Your Selenium Levels Are High?

If your water test shows elevated selenium levels, follow our selenium sampling flow chart to learn what to do next.

Need Help Treating Your Water?

Water Treatment Options to learn how to remove contaminants from your drinking water.

pH measures how acidic or basic (alkaline) water is. Pure water has a neutral pH of 7. Most drinking water falls between a pH of 6.5 and 8.5.

Changes in pH can affect how contaminants behave in your water. Understanding your water's pH helps you identify potential problems and maintain a safe water supply.

Low pH (Less Than 6.5)

Water that is too acidic can:

Leach harmful metals from pipes and plumbing
Increase levels of lead, manganese, copper, and iron
Cause these metals to enter your drinking water, which can be toxic in large amounts

High pH (More Than 8.5)

Water that is too basic (alkaline) can:

Taste bitter
Cause buildup of calcium and magnesium in pipes
Lead to dry, itchy, or irritated skin

High pH usually does not pose a health risk but may cause discomfort or plumbing issues.

How to Take a Water Sample:

What to Do If Your Water’s pH Is Outside the Normal Range?

If your pH test result is below 6.6 or above 8.5, check our pH sampling flow chart for what to do next.

Need Help Treating Your Water?

Water Treatment Options to learn how to remove contaminants from your drinking water.

Sulfates are a group of mineral salts that occur naturally or can be man-made. These salts can be found in soil, air, and water.

Drinking water with high levels of sulfate can cause diarrhea and dehydration, especially in people who are not used to it. Infants are particularly sensitive to high sulfate levels and may be more affected than adults.

How to Take a Water Sample:

What to Do If Your Sulfate Levels Are High?

If your sulfate test shows elevated levels, review our sulfate sampling flow chart to learn what to do next.

Need Help Treating Your Water?

Water Treatment Options to learn how to remove contaminants from your drinking water.

Uranium is a naturally occurring, mildly radioactive element found in rocks, soil, and water. In well water, uranium comes from the rock where the well is drilled.

Long-term exposure to high levels of uranium can damage the kidneys. However, the kidneys can recover once exposure is reduced or stopped.

Additional Resources:

How to Take a Water Sample:

What to Do If Your Uranium Levels Are High?

If your uranium test shows elevated levels, check our sampling flow chart to guide your next steps.

Need Help Treating Your Water?

Water Treatment Options to learn how to remove contaminants from your drinking water.

Lead can enter drinking water when it reacts with plumbing materials that contain lead. This chemical reaction, called corrosion, happens more easily when the water is acidic or has low mineral content.

Plumbing fixtures, pipe fittings, and solder (the material used to join pipes) that were installed before 1986 are more likely to contain lead.

High levels of lead in drinking water can be harmful to your health. If lead enters the bloodstream, it can cause serious health problems, including:

Damage to the brain and kidneys
Interference with the production of red blood cells, which carry oxygen throughout the body

Additional Resources:

How to Take a Water Sample:

What to Do If Your Lead Levels Are High?

If your lead test shows elevated levels, review our sampling flow chart for next steps.

Need Help Treating Your Water?

Water Treatment Options to learn how to remove contaminants from your drinking water.

About PFAS

Per- and polyfluoroalkyl substances (PFAS) are a group of thousands of man-made chemicals that have been used in products and industries worldwide since the 1940s. Long-term exposure to PFAS chemicals can have harmful effects on your health.

PFAS chemicals have been used in products such as:

Non-stick cookware
Water-repellent clothing
Stain-resistant fabrics and carpets
Some cosmetics
Some firefighting foams
Products that resist grease, water, and oil

During production, use, and disposal, PFAS can enter the soil, water, and air. Most PFAS chemicals do not break down, so they stay in the environment for a long time. As a result, PFAS are found in the blood of people and animals worldwide.

Additional Resources:

Need Help Treating Your Water?

Water Treatment Options to learn how to remove contaminants from your drinking water.

Ground Water Quality Near Me

The Idaho Department of Health and Welfare created this interactive map to help private well owners understand the quality of their ground water and encourage regular testing.

Ground water from private wells is not regulated by the State of Idaho. Private well owners are responsible for maintaining their wells and making sure their water is safe to drink. The best way to do this is by testing your water regularly.

About the Map

The map shows private wells that were sampled between 2004 and 2020 by the following agencies:

Idaho Department of Water Resources
Idaho Department of Environmental Quality
Idaho State Department of Agriculture
Private well owners

Each well on the map includes:

The most recent test results for up to nine chemicals
The year the water was sampled
The agency that collected the sample
The well depth, if known

Please note:
Some agencies may have additional data that is not shown on the map. Newer test results may exist for some chemicals. Contact the agency listed on the sample if you have questions or want more information.

How to Use the Map

Find a Location

Use the search box in the panel on the left side of the map to enter an address or place of interest.
By default, the map shows wells within two miles of your location. You can adjust this distance using the slider or the text box.

If you do not know the address, click the "Set Location" icon next to the magnifying glass. Then click anywhere on the map to choose a location.

View Well Results

Wells within your selected search area will appear below the slider.

If a well has test results that exceed a primary drinking water standard, it will be labeled "Primary Standard Exceeded."

Click on a search result or a well icon on the map to view the data. If multiple agencies sampled the same well or if a well was sampled in different years, use the arrows in the pop-up window to scroll through all available data.

Drinking Water Standards

Primary Standards

The following chemicals have primary drinking water standards:

Arsenic
Fluoride
Nitrate
Selenium
Uranium

These standards are set to protect human health. Public water systems are required to meet these standards. Private well owners should test their water and compare the results to these guidelines.

Units of measurement, such as micrograms per liter (ug/L) or milligrams per liter (mg/L), in the table may not match the units used in your lab report. If needed, convert the units so you can accurately compare your results.

Primary Chemical Standards and Health Effects

Chemical	Primary Standard	Health Effects
Arsenic	10 ug/L	Long term exposure to arsenic from drinking water can cause cancer and skin lesions.
Fluoride	4 mg/L	Depending on the length and amount of exposure, fluoride can stain teeth, increase risk of broken bones, or cause pain and tenderness in joints and bones.
Nitrate	10 mg/L	Nitrate can be converted to nitrite in humans where it lessens the ability of blood to carry oxygen. This is of greatest concern for infants, pregnant, and nursing women.
Selenium	0.05 mg/L	Prolonged exposure to elevated levels of selenium can cause fingernail or hair loss, numbness in extremities or circulation problems.
Uranium	30 ug/L	The greatest risk is kidney damage, especially for young children because their bodies are still developing.
Bacteria*	ZERO	Most coliform bacteria do not cause disease, but they can indicate the presence of other harmful bacteria such as Escherichia coli (E. coli). E. coli can cause nausea, vomiting, fever, and diarrhea. * Monitoring results related to bacteria were not included in this map because the presence of bacteria is typically a result of site specific conditions rather than a wide scale problem.

Secondary

The following chemicals are secondary drinking water standard that are not considered to present a risk to human health :

Chloride
Fluoride
Iron
Manganese
Sulfate

Secondary Chemical Standards and Health Effects

Chemical	Secondary Standard	Health Effects
Chloride	250 mg/L	Salty taste
Fluoride	2 mg/L	Tooth discoloration
Iron	0.3 mg/L	Rust color, sediment, metallic taste, reddish or orange staining
Manganese	0.05 mg/L	Black to brown color, black staining, or bitter metallic taste
Sulfate	250 mg/L	Salty taste

If you need help understanding or converting your test results, contact the laboratory that did the testing or call the Idaho Environmental Health Hotline at 1-800-445-8647. You can also email EH@dhw.idaho.gov.

Water Quality Testing Resources:

Chemical Testing Frequency

Testing	Chemical
Once a Year	Bacteria, Nitrate
Once every 3-5 years	Arsenic, Fluoride, Selenium, Uranium
If your water tastes, smells, or looks strange	Chloride, Manganese, Sulfate
If you live in an agricultural area and/or have underground tanks with petroleum	Pesticides, Petroleum
If you have a formula-fed infant under 6 months	Manganese

Fix a Problem

If there is a problem with your drinking water, you may need to disinfect your well, repair your system, find an alternative drinking water source, and/or install a water treatment device to remove contaminants. When installing a treatment system, look for NSF International certified treatment devices.

Treatment options for water for contaminants

Protecting Your Wellhead

Well maintenance and managing potential sources of contamination are very important to keep your water safe.

Inspect the well and surrounding area regularly:

Are the well casing, well cap, and surface seals intact and in good shape? Is the top of the well at least 18 inches above the ground?
Is the area around the well sloped to drain surface water away from the well?
Are irrigation valves set properly to prevent backflow?

Fertilizers, animal waste, pesticides, septic systems and other potential sources of contamination should be located and managed so they do not contaminate the well.

Avoid mixing or using fertilizers, herbicides, fuels, motor oil, and other pollutants near the well.
Do not pile snow, leaves, or other materials around the well.
Take care when working around the well to avoid damaging the casing.
Properly locate and manage septic systems.

Contribute Data

Private well owners utilizing the Idaho Bureau of Laboratories (IBL) as their testing laboratory have the opportunity to participate in citizen science by allowing their results to be displayed publicly on this map. Citizen science is the voluntary involvement of the public in scientific research, in this case data collection. This work helps professional scientists and other private well owners to better understand ground water quality in Idaho.

If you own a private well, consider becoming a citizen scientists by granting permission on IBL’s submission form to display your tests results on this map. There are more than 3,000 wells displayed on the map currently. Note data collected by citizen scientists may not have been collected under a Quality Assurance Project Plan (QAPP), a written document that outlines the procedures a monitoring project will use to ensure the samples collected are of high enough quality to meet project needs. Using a QAPP is not required to display your results, but resources are available online.