Testing Well Water: If your home gets its drinking water from a private well, testing your well water is your responsibility. Unlike public water systems, private wells are generally not regulated, treated, or routinely monitored under the federal Safe Drinking Water Act. (CDC)
That makes regular well-water testing one of the most important things a private well owner can do to protect household drinking water.
Well water can contain bacteria, nitrates, metals, chemicals, minerals, and naturally occurring substances that may not affect the appearance, taste, or smell of the water. A clear glass of water isn’t necessarily an indication that the water is safe.
The good news is that testing well water doesn’t have to be complicated. With the right testing schedule, a state-certified laboratory, and an understanding of local contamination risks, you can establish a practical water-quality monitoring program for your home.
This guide explains what to test for, how often to test, when additional testing is necessary, how to collect a sample, and what to do if a contaminant is detected.
Table of Contents: Testing Well Water
- Why Should You Test Well Water?
- How Often Should You Test Well Water?
- What Should You Test Well Water For?
- Annual Well Water Tests
- Additional Well Water Tests
- When Should You Test Your Well Water?
- How to Collect a Well Water Sample
- Where to Get Well Water Tested
- How Much Does Well Water Testing Cost?
- How to Read Well Water Test Results
- What If Your Well Water Fails a Test?
- Can You Use a Water Filter for Well Water?
- Is Reverse Osmosis Good for Well Water?
- Well Water Testing Checklist
- Frequently Asked Questions
- Final Thoughts
Why Should You Test Well Water?
Private well water comes from groundwater, which can be affected by natural geological conditions and activities occurring on or near your property.
Potential sources of well-water contamination include:
- Septic systems
- Agricultural fertilizers
- Pesticides and herbicides
- Animal waste
- Flooding
- Industrial activity
- Fuel storage
- Landfills
- Underground storage tanks
- Naturally occurring minerals and metals
- Changes to groundwater conditions
The CDC recommends that private well owners test their water at least annually for total coliform bacteria, nitrates, total dissolved solids (TDS), and pH. The agency also recommends working with local health or environmental departments to determine whether additional contaminants should be tested based on local conditions. (CDC)
Testing is important because many water contaminants cannot be detected by looking at, smelling, or tasting the water.
Well water isn’t automatically safe just because it looks clean.
Regular laboratory testing provides information that visual inspection alone cannot provide.
How Often Should You Test Well Water?
For most private wells, annual testing is a good minimum schedule.
The CDC and EPA recommend annual testing for key indicators including:
- Total coliform bacteria
- Nitrates
- Total dissolved solids
- pH
(CDC)
However, some situations warrant additional testing.
You should consider testing your well water sooner if:
- Your water changes color
- Your water develops a new odor
- Your water tastes different
- Your property floods
- Your well has been damaged
- You repair or replace well equipment
- Nearby construction changes the land
- There is a spill or chemical release nearby
- A septic system fails
- You are notified of a local groundwater problem
- Someone in your household becomes pregnant
- A young child begins living in the home
The CDC specifically recommends testing when you notice changes in your water or after events such as flooding or well-system repairs. (CDC)
What Should You Test Well Water For?
There isn’t one universal test panel that is appropriate for every private well.
The ideal testing program depends on:
- Your location
- Local geology
- Well depth
- Well construction
- Nearby land use
- Agricultural activity
- Septic systems
- Industrial activity
- Previous test results
- Local contamination concerns
A good starting point is the annual panel recommended by public-health agencies.
Then, add contaminant-specific testing based on local risks.
Annual Well Water Tests
1. Total Coliform Bacteria
Total coliform bacteria are commonly used as an indicator of potential contamination.
Coliform bacteria can enter groundwater through sources such as soil, surface water, animal waste, or sewage.
A positive result does not necessarily mean that a dangerous pathogen is present, but it can indicate that further investigation is needed.
The CDC recommends annual testing for total coliform bacteria. (CDC)
2. Nitrates
Nitrate is another important annual well-water test.
Nitrates can enter groundwater from sources such as:
- Fertilizer
- Animal waste
- Septic systems
- Wastewater
- Stormwater runoff
- Decaying vegetation
Elevated nitrate levels are particularly important for households with infants.
The CDC recommends testing private well water for nitrates at least once a year. (CDC)
3. pH
pH indicates how acidic or alkaline your water is.
While pH itself is not necessarily a direct measure of drinking-water safety, it can provide important information about water chemistry.
Water that is too acidic or otherwise corrosive can contribute to plumbing problems and may increase the potential for metals such as lead to enter water from plumbing components.
The CDC recommends annual pH testing for private wells. (CDC)
4. Total Dissolved Solids
Total dissolved solids (TDS) measure the concentration of dissolved material in water.
TDS can include substances such as:
- Calcium
- Magnesium
- Sodium
- Chloride
- Sulfates
- Bicarbonates
- Other dissolved minerals
TDS can affect taste, scaling, and the performance of water-treatment equipment.
It is important to remember that TDS is not a complete water-safety test.
A TDS reading cannot tell you exactly which contaminants are present.
For more information about measuring TDS, see Revosmo’s guide to TDS Meters Explained.
Additional Well Water Tests
Depending on where you live and the conditions surrounding your well, you may need additional testing.
Lead
Lead can enter drinking water through plumbing materials and can also be present in private well systems.
Testing is the only way to determine whether lead is present in your drinking water. The CDC recommends using an approved sampling protocol and a certified laboratory when testing for lead. (CDC)
Arsenic
Arsenic can occur naturally in groundwater depending on local geology.
Some regions have naturally elevated arsenic concentrations, making location-specific testing particularly important.
Radium and Other Radionuclides
Certain groundwater sources may contain naturally occurring radioactive substances.
EPA guidance notes that private well owners may need periodic testing for radionuclides depending on local conditions. (US EPA)
Your state or local health department can help determine whether radionuclide testing is appropriate for your area.
Radon
Radon can occur naturally in groundwater and may be a concern in certain geological regions.
If your local health department identifies radon as a potential groundwater concern, consider adding it to your testing program.
VOCs
Volatile organic compounds (VOCs) include a wide range of chemicals associated with industrial activity, fuels, solvents, and other sources.
Potential VOC concerns can depend heavily on what is happening around your property.
The CDC specifically recommends asking local health or environmental officials whether VOC testing is appropriate for your well. (CDC)
Pesticides and Herbicides
If your property is near agricultural land or areas where pesticides and herbicides are used, these chemicals may warrant consideration.
Your local health department or environmental agency can help identify which compounds are relevant to your area.
Fluoride
Naturally occurring fluoride levels can vary by location.
If fluoride is a concern in your region, consider including it in your laboratory testing.
Manganese and Iron
Iron and manganese are common groundwater concerns.
They can cause:
- Metallic taste
- Staining
- Discoloration
- Deposits
- Water-treatment problems
They aren’t necessarily indicators of a serious health problem at typical concentrations, but elevated levels can affect water quality and household plumbing.
When Should You Test Your Well Water?
Timing matters.
Test Every Year
Establish a recurring annual testing schedule.
Testing at approximately the same time each year makes it easier to compare results over time.
The CDC recommends annual testing for total coliform bacteria, nitrates, TDS, and pH. (CDC)
Test After Flooding
Floodwater can introduce contaminants into a well.
If your well has been affected by flooding, contact your local health department about appropriate testing and precautions.
EPA guidance specifically recommends testing wells after flooding. (US EPA)
Test After Well Repairs
If you repair or replace components of your well system, testing afterward can help confirm that the system hasn’t been compromised.
Test When Water Changes
A sudden change in:
- Taste
- Odor
- Color
- Cloudiness
is a good reason to investigate.
A change doesn’t necessarily mean that the water is dangerous, but it should not be ignored.
How to Collect a Well Water Sample
Proper sample collection is essential.
Even an excellent laboratory can produce a misleading result if the sample is contaminated or collected incorrectly.
Step 1: Contact the Laboratory
Before collecting your sample, ask the laboratory about its sampling requirements.
Different tests may require different bottles, preservatives, collection methods, or shipping procedures.
Step 2: Use the Correct Container
Use the container provided or approved by the laboratory.
Don’t substitute an ordinary household container unless the laboratory specifically says it is acceptable.
Step 3: Follow Sampling Instructions
The laboratory may provide instructions regarding:
- Which faucet to use
- Whether to remove aerators
- How long to run the water
- Whether to disinfect the faucet
- How full to fill the bottle
- Whether preservatives are required
Follow these instructions exactly.
Step 4: Avoid Contamination
Don’t touch the inside of the sample bottle or its cap.
Keep the bottle away from dirt, chemicals, cleaning products, and other potential sources of contamination.
Step 5: Return the Sample Promptly
Some water tests have strict holding-time requirements.
Follow the laboratory’s instructions for delivery or shipping.
Where to Get Well Water Tested
Use a state-certified laboratory for drinking-water testing.
The CDC and EPA both recommend using certified laboratories for private well testing. (CDC)
Your local or state health department may provide:
- Lists of certified laboratories
- Recommended testing panels
- Sampling instructions
- Information about local contaminants
- Assistance interpreting results
This local information can be extremely valuable because groundwater chemistry varies considerably from one region to another.
How Much Does Well Water Testing Cost?
The cost depends heavily on what you’re testing for.
A basic test for common indicators may cost considerably less than a comprehensive laboratory panel testing for dozens of chemicals.
Additional costs may apply for tests involving:
- PFAS
- VOCs
- Radionuclides
- Pesticides
- Heavy metals
- Specialized microorganisms
Rather than automatically purchasing the largest available test package, ask your local health department or a certified laboratory which contaminants make sense for your location.
This can help you spend money on testing that provides useful information.
How to Read Well Water Test Results
A laboratory report may include several important pieces of information.
Look for:
- Contaminant name
- Concentration
- Measurement units
- Detection limit
- Applicable drinking-water standard
- Sample date
- Laboratory method
- Whether the result exceeded a relevant standard
Common units include:
- mg/L
- µg/L
- ppm
- ppb
- pCi/L
Don’t compare a result with a regulatory limit until you’ve confirmed that the units are the same.
Example
Suppose a laboratory reports:
Nitrate: 5 mg/L
You would then compare that result with the appropriate drinking-water benchmark.
For a more comprehensive explanation of interpreting water-testing information, visit Revosmo’s How to Test Your Drinking Water guide.
What If Your Well Water Fails a Test?
If a test indicates that your water contains a contaminant above an applicable health standard, don’t immediately assume that buying a particular filter is the correct solution.
Start by confirming the result and getting professional guidance.
Step 1: Contact Your Health Department
Your local or state health department can help interpret the result and determine what should happen next.
Step 2: Confirm the Result
Depending on the contaminant, a repeat sample may be appropriate.
Step 3: Identify the Source
The contamination may originate from:
- The aquifer
- The well
- A septic system
- Plumbing
- Agricultural activity
- Nearby industrial activity
- Natural geological conditions
Step 4: Determine the Appropriate Treatment
Treatment should be selected based on the specific contaminant.
Different filtration technologies remove different substances.
Step 5: Retest
After corrective action, retesting can confirm whether the problem has been addressed.
EPA guidance recommends contacting the appropriate public-health department and having the well retested when a contaminant exceeds a health standard. (US EPA)
Can You Use a Water Filter for Well Water?
Yes.
Water treatment can be an effective way to address specific well-water problems, but the treatment system should be selected based on actual test results.
Possible treatment technologies include:
| Water Problem | Potential Treatment |
| Sediment | Sediment filter |
| Bacteria | Disinfection, UV, or other appropriate treatment |
| Hardness | Water softener |
| Iron | Iron-specific treatment |
| Manganese | Manganese-specific treatment |
| Chlorine | Activated carbon |
| Certain dissolved contaminants | Reverse osmosis |
| Specific chemical contaminants | Contaminant-specific treatment |
This table is a general guide, not a recommendation for a particular installation.
Always verify that the treatment system is appropriate for the contaminant and concentration found in your water.
Is Reverse Osmosis Good for Well Water?
Reverse osmosis can be useful for treating certain contaminants found in well water, particularly at the point of use.
However, an RO system should not automatically be considered the solution to every well-water problem.
For example, if your well has:
- High sediment
- Iron
- Manganese
- Severe hardness
- Bacteria
- Low water pressure
you may need pretreatment or another treatment technology before or alongside an RO system.
A properly designed system may combine several treatment stages.
For example:
Well → Sediment Filtration → Pretreatment → RO → Post-Filtration → Drinking Faucet
The appropriate configuration depends on your test results and water chemistry.
For a detailed explanation of reverse osmosis technology and system components, read Revosmo’s The Ultimate Guide to Reverse Osmosis Systems.
Well Water Testing Checklist
Use this checklist to establish a basic testing routine.
Every Year
☐ Test total coliform bacteria
☐ Test nitrates
☐ Test pH
☐ Test total dissolved solids
☐ Inspect the well and surrounding area
☐ Review previous test results
Consider Additional Testing For
☐ Lead
☐ Arsenic
☐ Radon
☐ Radium
☐ Uranium
☐ Iron
☐ Manganese
☐ Fluoride
☐ VOCs
☐ Pesticides
☐ Herbicides
☐ PFAS
☐ Other locally relevant contaminants
Test Immediately After
☐ Flooding
☐ Well damage
☐ Well repairs
☐ Septic-system problems
☐ Nearby chemical spills
☐ Significant land disturbance
☐ Changes in taste
☐ Changes in odor
☐ Changes in color
The exact testing schedule should be adapted to your location and well conditions.
Frequently Asked Questions About Testing Well Water
How often should I test my well water?
At minimum, the CDC recommends testing private well water every year for total coliform bacteria, nitrates, TDS, and pH. Additional testing may be appropriate depending on local conditions. (CDC)
What is the most important well-water test?
There isn’t one test that is most important for every well. Total coliform bacteria and nitrates are important annual tests, while other contaminants should be selected based on local geology, land use, and known risks.
Can I test my well water myself?
Home test kits can be useful for screening some water characteristics, but laboratory testing is generally preferable when you need reliable results for drinking-water decisions. Use a state-certified laboratory for formal drinking-water testing. (CDC)
How do I know what to test for?
Contact your local or state health department and ask which contaminants are common in your area. The appropriate testing panel depends on your location and potential sources of contamination.
Should I test well water after flooding?
Yes. Flooding can introduce contaminants into a private well. Contact your local health department for guidance about testing and whether the well should be disinfected or otherwise treated. (US EPA)
Does well water need to be filtered?
Not necessarily. The need for filtration depends on the results of your water testing and the specific characteristics of your water.
Is reverse osmosis good for well water?
RO can reduce many dissolved substances and can be useful for certain well-water problems. However, well water with sediment, iron, manganese, hardness, bacteria, or other issues may require pretreatment or additional treatment.
Can TDS testing tell me if well water is safe?
No. TDS is a general measurement of dissolved material. It does not identify individual contaminants or prove that water is safe to drink.
What should I do if my well water test is positive for bacteria?
Contact your local health department or a qualified water professional for guidance. Depending on the specific result and circumstances, disinfection or other corrective measures may be appropriate. Retesting is important to confirm that the problem has been resolved.
Final Thoughts
Testing well water should be a regular part of private well ownership.
Because private wells aren’t covered by the same federal regulatory framework as public drinking-water systems, homeowners have an important role in monitoring their water quality. (CDC)
At a minimum, establish an annual testing routine that includes total coliform bacteria, nitrates, pH, and total dissolved solids. Then work with your local health department to determine whether additional testing for contaminants such as arsenic, lead, radon, VOCs, pesticides, or radionuclides makes sense for your location. (CDC)
Don’t wait until your water tastes strange or looks cloudy before testing. Some contaminants can be present without producing an obvious change in the water.
For a broader guide to choosing tests, understanding testing methods, and evaluating drinking-water quality, read Revosmo’s How to Test Your Drinking Water.
If your test results indicate that filtration is necessary, the next step is to match the treatment technology to the specific contaminants found. For homeowners considering reverse osmosis, Revosmo’s The Ultimate Guide to Reverse Osmosis Systems explains how RO works and what to consider when selecting a system.
