Blog Post

If you get your drinking water from a private well, there is something you need to know: no government agency is monitoring your water quality. Unlike public water systems, which are regulated by the EPA and tested regularly, private wells are entirely the responsibility of the homeowner. That means the safety of your family’s drinking water depends on you.

This guide covers what private well owners should test for, how often to test, and how to collect and submit samples to a certified laboratory like AATLS.

Why Private Well Owners Are Responsible for Their Own Water Quality

The U.S. Environmental Protection Agency (EPA) does not regulate private wells. The Safe Drinking Water Act, which sets standards for public water systems across the country, simply does not apply to individual residential wells. That leaves an estimated 43 million Americans — roughly 15 percent of the U.S. population — without any automatic water quality monitoring or enforcement.

This does not mean private well water is inherently unsafe. Many wells produce clean water for decades. However, without regular water testing, there is no way to know whether your water is safe. Contamination can develop gradually and go undetected for years because many harmful contaminants have no taste, odor, or visible signs.

Common sources of well water contamination include:

• Agricultural runoff: Pesticides, herbicides, and fertilizers (particularly nitrates) can seep into groundwater from nearby farms and ranches.
• Septic systems: A failing or poorly maintained septic system can introduce bacteria, nitrates, and other pathogens into nearby groundwater.
• Natural geology: Minerals like arsenic, uranium, radon, and manganese occur naturally in certain rock formations and can dissolve into groundwater at harmful concentrations.
• Flooding and surface runoff: Heavy rains and flooding events can wash surface contaminants directly into wells, especially older or improperly sealed wells.
• Industrial activity: Past or present industrial operations near your property may have released chemicals like volatile organic compounds (VOCs) or heavy metals into the ground.

Because no one else is checking, the burden falls entirely on the homeowner to test regularly and take corrective action when problems are found.

Recommended Annual Tests: Bacteria, Nitrates, pH, and More

At a minimum, the EPA and most state health departments recommend testing your private well water once per year for several core parameters. These baseline tests provide a snapshot of your water’s safety and can catch common problems early.

Core Annual Tests

• Total coliform bacteria: An indicator organism whose presence signals a pathway exists for harmful organisms to enter your water supply. If detected, follow-up testing for E. coli is essential.
• E. coli: A serious finding indicating fecal contamination and immediate health risk. If detected, stop drinking the water and take corrective action right away.
• Nitrate: Nitrate contamination is particularly dangerous for infants under six months of age, as it can cause methemoglobinemia (blue baby syndrome). The EPA’s maximum contaminant level (MCL) for nitrate is 10 mg/L. Sources include agricultural fertilizers, animal waste, and septic systems.
• pH: While pH itself is not a health hazard, water that is too acidic (below 6.5) or too alkaline (above 8.5) can corrode plumbing, leach metals like lead and copper into your water, and affect the effectiveness of disinfection.
• Total dissolved solids (TDS): TDS measures the total concentration of dissolved minerals, salts, and metals. While not typically a direct health concern, elevated TDS can affect taste and may indicate other water quality issues worth investigating.

Additional Tests Based on Your Region

Depending on where you live and the geology of your area, additional testing may be strongly recommended:

• Arsenic: Naturally occurring in groundwater across much of the western U.S., including significant portions of Arizona. The EPA MCL is 10 ppb. Chronic exposure above this level is associated with increased cancer risk.
• Uranium: Like arsenic, uranium occurs naturally in certain geological formations common in Arizona and the Southwest. Long-term exposure can affect kidney function.
• Radon: A radioactive gas that can dissolve into groundwater and be released into indoor air during showering and other water use. Radon in water is a concern in areas with granite bedrock.
• Iron and manganese: While not typically health hazards at common levels, these metals cause staining, unpleasant taste, and can promote bacterial growth in plumbing.
• Lead: Usually enters water from older plumbing rather than the well itself. Testing at the tap is the best way to assess lead exposure.

For well owners in Arizona specifically, arsenic and uranium testing should be considered essential additions to your annual testing program. The geology of southern and central Arizona makes these contaminants a real and well-documented concern.

When to Test More Frequently

Annual testing is the recommended baseline, but certain situations call for immediate or more frequent testing. Do not wait for your next scheduled test if any of the following apply:

• After flooding or heavy rain: Flood events are a common cause of sudden well contamination. Surface water can enter wells through cracks, improper seals, or wellhead damage. Test for bacteria and nitrates at a minimum.
• After well repair or maintenance: Any time your well pump is pulled, the casing is opened, or repairs are made to the well system, test your water before resuming use. Construction and repair activities can introduce contaminants.
• Nearby land use changes: New construction, agricultural operations, mining activity, or industrial development near your property can affect groundwater quality. If you notice new activity within a half-mile of your well, consider testing.
• Changes in taste, odor, or appearance: Any noticeable change in your water — a new smell, unusual taste, discoloration, or cloudiness — should prompt immediate testing. These changes can indicate bacterial contamination, mineral intrusion, or chemical contamination.
• Pregnancy or a new infant in the home: Pregnant women and infants are more vulnerable to certain contaminants, particularly nitrates and lead. If you are expecting a child or have a newborn, test your well water to confirm it is safe.
• Real estate transactions: If you are buying or selling a property with a private well, a comprehensive water test is a smart investment. Many mortgage lenders require well water testing, and the results can be a significant factor in negotiations.

How to Collect and Submit Well Water Samples

Accurate water test results depend on proper sample collection. Contamination introduced during sampling can lead to false positives, while improper technique can miss real problems. Here is how to collect a reliable well water sample:

Step-by-Step Sampling Procedure

1. Choose the right tap: Collect from a cold water tap connected directly to your well system, before any treatment or filtration. A kitchen faucet or outdoor spigot near the pressure tank is ideal. Remove any aerator or filter first.
2. Sterilize the tap: For bacteriological samples, sterilize the faucet opening with a flame (a lighter works) or wipe it thoroughly with an alcohol-soaked cloth. This prevents false positive results from bacteria on the fixture itself.
3. Flush the line: Run the cold water for at least two to three minutes before collecting your sample. This clears standing water from the pipes and ensures you are sampling water directly from the well.
4. Fill the container properly: Use only laboratory-provided sample containers. Fill them according to the instructions — some containers contain preservatives and should not be overfilled or rinsed. For bacteria samples, leave a small air space in the bottle.
5. Label and document: Record the date, time, sample location, and your name on each container. Complete the chain of custody form included with your sampling kit.

Shipping and Handling

Once collected, water samples should be kept cool (not frozen) and shipped to the laboratory as quickly as possible. Bacteria samples in particular have a strict holding time — typically 24 to 30 hours from collection to analysis. Use the insulated shipping container and cold packs provided in your sampling kit, and ship via overnight delivery.

What to Expect in Your Results

Your laboratory report will list each parameter tested, the result, the unit of measurement, and the applicable regulatory limit (such as the EPA MCL). Results will be clearly flagged if they exceed any health-based standard. A well-prepared report should be understandable even if you do not have a science background.

How AATLS Makes It Easy

At AATLS, we simplify the entire process for private well owners. When you submit a sample, here is what you can expect:

• Sampling kits shipped to your door: We send you everything you need — pre-labeled bottles, preservatives, chain of custody forms, collection instructions, and an insulated return shipping container.
• Fast turnaround: Most well water test results are available within 3 to 5 business days after the lab receives your sample.
• Clear, detailed reports: Our reports are designed to be readable and actionable, with results compared against EPA and state standards.
• Expert support: If you have questions about your results or need guidance on next steps, our team is available to help.

As an ISO 17025 accredited and CDC ELITE certified laboratory, AATLS delivers results you can trust. We serve well owners across Arizona and nationwide.