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If you want to know whether your water is suitable for drinking or another household use, the best place to have it tested is a certified drinking-water laboratory. Your local health department, environmental agency, or water utility can usually help you find one.
In the United States, the EPA recommends using a state-certified laboratory for independent drinking-water testing. The EPA does not test residential water samples itself.
The right test depends on where your water comes from and what you plan to do with it. Rainwater, private well water, and city water can have very different concerns.
Where You Can Have Water Tested
A certified drinking-water laboratory
A certified laboratory is usually the best choice when the results will affect a health decision.
These labs use approved testing methods and have requirements for quality control. In the United States, states certify laboratories for specific drinking-water tests. A lab may be certified for bacteria testing but not for every metal, pesticide, or other contaminant.
You can find one through your state's drinking-water laboratory certification program. The EPA maintains contact information for these programs.
When you call a laboratory, tell them:
- Where the water comes from
- Whether you drink it
- Whether it has been treated
- Why you want it tested
- Whether you have noticed a change in color, smell, or taste
- Whether there has been flooding, construction, contamination, or a system repair
The lab can then tell you which tests it performs and how the sample must be collected.
Your local or county health department
A health department is a good starting point, especially for private wells.
Some health departments collect samples themselves. Others provide sampling containers or direct homeowners to approved laboratories. They may also know which contaminants are common concerns in the local area.
The CDC recommends asking your health or environmental department which additional contaminants should be tested based on local conditions.
Your state environmental or drinking-water agency
State agencies often maintain searchable lists of certified laboratories.
This can be especially useful if you need testing for something specific, such as:
- Coliform bacteria
- Nitrate
- Lead
- Arsenic
- Iron or manganese
- Volatile organic compounds
- Pesticides
- Other locally important contaminants
Do not assume every laboratory tests for everything. Certification can apply to individual test methods or contaminants.
Your water utility
If you receive city or community water, start by checking with your water utility.
Public water systems regularly test the water they supply. They also provide water-quality information to customers. However, a utility's system-wide results do not necessarily tell you what is happening inside your home's plumbing.
For example, lead can enter water from service lines, pipes, fittings, or faucets. Testing water from the actual tap is the way to determine whether lead is present at that sampling point.
Where Should Rainwater Be Tested?
If you collect roof runoff, use a laboratory that is able to analyze drinking-water samples when the water may eventually be used for drinking, cooking, or other potable uses.
Potable means suitable for drinking. Non-potable water is water intended for uses such as irrigation or toilet flushing rather than drinking.
Tell the laboratory that the source is collected rainwater. That matters because a rainwater system can pick up contaminants at several points:
Roof → gutters → first-flush or debris controls → tank → pump → filters or treatment → plumbing → tap
Roof runoff can collect dust, animal droppings, leaves, particles, and material from roofing and other surfaces. Storage tanks and plumbing can introduce other water-quality problems.
A laboratory test should therefore match the intended use of the water and the possible contamination sources in your particular system.
For a system intended to supply drinking water, do not depend on a single bacteria test, TDS reading, filter, UV unit, or home test strip to declare the water safe. Drinking-water use requires suitable collection, treatment, laboratory testing, maintenance, and compliance with applicable local requirements.
Where Should You Take the Sample?
That depends on what you are trying to learn.
Testing the stored water
Take a properly collected sample from the storage system if you want to understand the quality of the water in the tank.
This might help investigate contamination entering through the roof, gutters, tank, overflow, vents, or other parts of the collection system.
Testing treated water
Sample after the treatment system if you need to know the quality of the treated water.
For a system intended for drinking, the point-of-use tap is often important because it represents the water a person actually receives.
Comparing before and after treatment
Sometimes separate samples before and after treatment can help show where a problem is occurring.
For example, bacteria found before treatment but not afterward gives different information than bacteria found at the household tap.
Do not make up your own sampling method, especially for bacteria, lead, or other tests with strict collection rules. Ask the laboratory where and how to collect each sample.
What Should You Have Your Water Tested For?
There is no single test panel that is right for every water source.
The right tests depend on:
- Water source
- Intended use
- Local geology and land use
- Roof and plumbing materials
- Nearby septic systems or agriculture
- Flooding or runoff
- Past laboratory results
- Changes in smell, taste, or appearance
- Treatment equipment already installed
For private wells, CDC guidance recommends testing at least annually for total coliform bacteria, nitrate, total dissolved solids, and pH, while also asking local health officials about other contaminants of concern.
That list should not automatically be copied to every rainwater system. Rainwater has different contamination pathways than groundwater.
What is TDS?
Regarding home drinking-water test equipment, verify the cleaning or replacement step justified by test evidence.
Total dissolved solids, or TDS, is a measure of dissolved substances in water.
A TDS meter can be useful for noticing changes, but TDS does not identify individual contaminants. Low TDS does not prove that water is safe to drink. Bacteria and some chemicals can be present even when the TDS number looks low.
What about bacteria?
Microbiological testing is especially important when contamination by animals, sewage, surface runoff, or poorly protected storage is possible.
The laboratory may provide special sterile sample bottles and detailed collection instructions. Follow those instructions exactly. Touching the inside of a bottle or cap, using the wrong faucet, or delaying delivery can affect the result.
Can I Use a Home Water Test Kit Instead?
Home tests can be useful for screening or routine system checks, but they are not a substitute for laboratory testing when the result will determine whether water is safe to drink.
A home test may measure one or several things, such as:
- pH
- Hardness
- Chlorine
- Nitrate
- Iron
- TDS
Different tests have different limits.
A strip showing a normal-looking result does not rule out contaminants the strip does not measure. Likewise, a TDS meter cannot tell you whether water contains harmful bacteria, lead, arsenic, pesticides, or many other contaminants.
Use a certified laboratory when you need reliable drinking-water results.
How to Choose a Water Testing Laboratory
Before sending a sample, contact the laboratory and ask whether it is certified or otherwise officially accredited for the specific drinking-water analyses you need.
Also ask:
- Which tests are appropriate for your water source and intended use?
- Does the lab provide its own sample bottles?
- Are any bottles supplied with preservatives already inside them?
- Where should each sample be collected?
- Does the water need to sit unused before sampling?
- Does the sample need refrigeration?
- How quickly must it reach the laboratory?
- Will the report explain the units and applicable drinking-water standards?
Sampling instructions can be just as important as the analysis.
For example, EPA guidance for lead testing tells homeowners to carefully follow the laboratory's instructions and collect samples from faucets used for drinking.
Never rinse out a laboratory bottle unless the laboratory specifically tells you to do so. Some bottles are sterile or contain preservatives needed for the test.
When Should You Have Water Tested?
Testing is useful when establishing a baseline for a new water source and whenever conditions change.
Consider laboratory testing after:
- Flooding
- Major repairs
- A new tank or plumbing installation
- Changes to treatment equipment
- A noticeable change in taste, odor, or color
- Possible chemical contamination
- An animal or debris entering the storage system
- Long periods when the system was unused
Private-well owners should also follow an ongoing testing schedule. The CDC recommends testing private well water at least once each year and testing again when certain changes or contamination events occur.
For rainwater used as drinking water, the testing schedule should be based on the complete system, local requirements, treatment method, risks around the catchment, and advice from qualified water-quality professionals.
What If the Laboratory Finds a Problem?
Do not immediately buy a filter based only on the name of the contaminant.
First determine:
- What was detected
- At what concentration
- Whether the sample was collected correctly
- Whether the result has a health-based standard or guideline
- Where the contaminant may be entering the system
- Whether additional or confirmation testing is needed
EPA guidance for private wells recommends contacting the public health department when a contaminant exceeds a health standard and having the water retested as appropriate.
Treatment must match the contaminant. A sediment filter, for example, works on particles but should not be assumed to remove dissolved chemicals or microorganisms. UV treatment works differently from filtration and also has operating and maintenance requirements.
If the water may be unsafe to drink, use an appropriate alternative drinking-water source while you get qualified guidance rather than relying on an unverified treatment change.
Finding a Lab Near You
As of August 31, 2026, U.S. homeowners can use the EPA's directory of state laboratory certification programs to locate certified drinking-water laboratories.
You can also contact your:
- Local health department
- County environmental health office
- State drinking-water agency
- State environmental agency
- Public water utility
Outside the United States, look for laboratories accredited or approved for drinking-water analysis by your national, regional, or local health or environmental authority.
For rainwater systems, tell the laboratory that you are testing harvested rainwater and explain whether the water will be used for irrigation, household non-potable use, or drinking. That gives the laboratory much better information than simply asking for a "water test."
Frequently Asked Questions
Can a hardware store test my water?
Some stores may offer basic screening or arrange testing through another company. For decisions about drinking-water safety, use a laboratory certified or officially accredited for the specific drinking-water tests you need.
Can my local health department test my water?
Possibly. Some health departments offer testing, provide sample kits, or direct residents to certified laboratories. Your local health department is also a good place to ask which contaminants are important in your area.
Can I send rainwater to a regular water-testing laboratory?
Yes, if the laboratory performs the tests you need. Tell the lab that the sample is harvested rainwater and explain its intended use. For drinking-water decisions, use a laboratory qualified for drinking-water analysis.
How do I know which contaminants to test for?
Start with your water source, intended use, local contamination risks, system materials, and any symptoms such as unusual color or odor. A certified laboratory or local health department can help choose appropriate tests rather than testing randomly.
Is a TDS test enough to tell whether water is safe?
No. TDS measures the amount of dissolved material but does not identify what those substances are. It also does not provide a complete test for bacteria, metals, pesticides, or other contaminants.
Should I test water before or after my filters?
It depends on your goal. Testing untreated and treated water can help evaluate where contamination occurs, while testing at the drinking-water tap tells you about the water reaching the user. Ask the laboratory how each sample should be collected.
Does clear, good-tasting water still need testing?
It can. Many contaminants cannot be identified by sight, smell, or taste. If water comes from a private source or rainwater system and will be used for drinking, appearance alone cannot establish that it is safe.
