There are two types of people who should test their water: people on private wells (essentially everyone, regularly), and people on municipal water who have specific concerns: they live near an industrial site, their pipes are old, they've gotten a notice from their utility, or they simply want to know what's coming out of their tap.
Water testing is not complicated, but doing it correctly matters. A bad sample collection technique can produce inaccurate results, and testing for the wrong things wastes money. Here's how to do it right.
Step 1: Decide What You're Testing For
You cannot test for "everything" in any meaningful sense. There are thousands of potential water contaminants. You need to choose a panel based on your specific situation:
- Private well, rural area: Test for bacteria (coliform, E. coli), nitrates, pH, hardness, and arsenic at minimum. If you're near agriculture, add pesticides. The EPA recommends annual testing for bacteria and nitrates, more frequently after flooding or nearby construction.
- Older home (pre-1986 plumbing): Test for lead. Lead doesn't come from your utility; it comes from your home's own pipes and solder. A utility that passes its tests can still have elevated lead at your tap if your plumbing is old.
- Near a military base, airport, or industrial site: Test for PFAS. This is a separate panel; most standard water tests don't include PFAS. You need to specifically request it.
- Getting a basic check on municipal water: A standard panel covering bacteria, lead, nitrates, pH, hardness, chlorine byproducts (trihalomethanes), and a few heavy metals runs $30-$75 at most certified labs.
- PFAS-specific test: A full PFAS panel (testing for 20+ compounds) costs $150-$300 at certified labs.
Step 2: Use a State-Certified Lab
This is the most important step most people skip. The EPA maintains a directory of certified labs for every state at epa.gov/dwlabcert. Your state health department also maintains its own list. Use one of these labs, not a home kit from a hardware store.
Home test kits (the kind with strips or chemical reagents) can give a rough indication of pH, hardness, and sometimes nitrates, but they are not accurate enough for lead or PFAS, and they can't test for bacteria at all. If you want results you can actually act on, use a certified lab.
Many certified labs will mail you a sampling kit. You collect the sample at home following their specific instructions and mail it back. Results typically arrive within 5-10 business days.
Step 3: Collect the Sample Correctly
Incorrect sampling is the most common source of misleading results. The instructions from your certified lab take precedence over anything else; follow them exactly. General principles:
- For lead testing: Collect a "first draw" sample: the water that has been sitting in your pipes for at least six hours (overnight is ideal), without running the tap first. This captures lead that may have leached from your plumbing while the water was still. Many utilities collect samples after flushing, which underestimates lead at the tap.
- For bacteria testing: Use the sterile container provided by the lab. Do not rinse it. Run the tap for 30 seconds first to clear the aerator, then collect the sample. Bacteria can be introduced from the aerator or from your hands touching the container.
- For PFAS testing: Use only the containers provided by the lab. PFAS testing is sensitive to contamination from plastic containers that aren't specifically designed for the purpose. Some labs prefer glass containers for PFAS samples.
- For everything else: Run the tap for 30-60 seconds before collecting. You want water from the main supply, not from pipes that have been sitting idle.
Step 4: Read the Results
Your lab report will list each contaminant tested, the level found (usually in mg/L, ppb, or ppt depending on the compound), and the EPA's Maximum Contaminant Level (MCL) for comparison. Some labs will flag any result above the MCL in red.
Key things to know when reading results:
- MCLs are legal limits, not zero-risk thresholds. For some contaminants (lead, PFAS), the EPA acknowledges there is no fully safe level; the MCL reflects what's achievable with current treatment technology. "Below MCL" doesn't always mean "no concern."
- Lead action level vs. MCL: Lead doesn't have a traditional MCL. Instead, the EPA uses an "action level" of 15 ppb, meaning if more than 10% of samples from high-risk homes exceed this, the utility must take action. The current thinking in public health is that any measurable lead in children's drinking water is a concern, regardless of the action level.
- PFAS reporting: The new EPA MCLs are 4 ppt for PFOA and PFOS. Some labs report combined PFAS levels; others break out individual compounds. Make sure you understand what the lab is measuring and reporting.
Step 5: Act on What You Find
If results come back above MCLs or with concerning levels:
- Lead above 5 ppb: Stop drinking unfiltered tap water for cooking and drinking. Install an NSF/ANSI 53-certified filter or reverse osmosis system rated for lead removal. Run cold water for 1-2 minutes before using it each morning. Contact your local health department.
- PFAS above 4 ppt: Reverse osmosis systems and NSF/ANSI 58-certified activated carbon block filters are the most effective at removing PFAS. Note: pitcher filters and standard carbon filters have inconsistent PFAS removal rates; look specifically for filters certified under NSF 58 for PFAS reduction.
- Bacteria detected: Stop using the water for drinking and cooking until the source is identified. Boiling kills bacteria but doesn't remove chemical contaminants. Contact your county health department and, if you're on a well, a licensed well contractor.
- Nitrates above 10 mg/L: Do not give this water to infants under 6 months old. Reverse osmosis removes nitrates effectively.
How Often to Test
For municipal water users: once when you move into a home, particularly for lead if it's pre-1986 construction, and whenever you have a specific concern. After major flooding. If you receive a notice from your utility about a violation. If you notice a change in taste, odor, or color.
For well users: bacteria and nitrates annually at minimum. Full panel every 3-5 years or any time you notice changes. Immediately after any flooding that affects the well.
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