How accurate are home arsenic test strips?

Not accurate enough for health decisions. Most home test strips detect arsenic down to about 10-50 ppb, but their sensitivity varies. At 12 ppb, above the EPA limit of 10 ppb, many strips will show a negative result. A false negative doesn't mean your water is safe. Use a certified lab test for any result you'll base health decisions on.

How much does a lab arsenic test cost?

An arsenic-specific lab test typically costs $15 to $50 at a state-certified lab. Some labs include arsenic in broader well water panels that cost $75-150 and cover heavy metals, nitrates, bacteria, and other parameters. If you've never tested your well at all, the broader panel is worth the extra cost to get a full picture.

How long does arsenic testing take?

Most certified labs return results within 3-7 business days after receiving your sample. Some offer expedited processing for an additional fee. Mail-in services typically include a prepaid return envelope. You collect the sample and mail it same day or the next day.

Do state health departments offer free arsenic testing?

Some do. Maine, New Hampshire, and New Mexico have run programs offering subsidized or free arsenic testing for private well owners. Program availability changes year to year depending on funding. Contact your state's drinking water or environmental health program directly to ask what's currently available for your county.

What arsenic level is safe in well water?

The EPA's Maximum Contaminant Level for arsenic in public water is 10 ppb (micrograms per liter). The MCLG, the health-based goal, is zero, meaning no level is definitively risk-free. If your well tests above 10 ppb, treatment is warranted. Below 10 ppb is within federal limits but still carries some long-term risk. The EPA sets 10 ppb as the limit for public systems because that's what's technically and economically achievable, not because it's a threshold where risk disappears.

How to Test Your Well Water for Arsenic

Health disclaimer: This page provides general information about arsenic testing in private wells. It is not medical advice. If you have concerns about arsenic exposure or health symptoms, contact your doctor and your local health department. Private well owners are responsible for their own water quality monitoring.

The EPA sets arsenic’s limit for public water at 10 ppb. Your private well has no such monitoring. If you’re in Maine, New Hampshire, Arizona, Nevada, or rural parts of the Midwest, the odds your well contains detectable arsenic are higher than in most of the country. The only way to know your level is to test.

That part’s straightforward. What trips people up is choosing the wrong test method and getting a result they can’t trust.

Why You Need a Lab Test, Not a Strip

Home arsenic test strips are sold at hardware stores and online for around $10-20 for a pack. They seem convenient. The problem is their detection limits.

Most strips can’t reliably detect arsenic below 10-50 ppb. The EPA’s limit is 10 ppb. That means a strip might show you a clean result at 12 ppb, which is above the federal limit for public water. You’d never know.

This isn’t a hypothetical failure mode. The detection gap is built into the chemistry of colorimetric strip tests. They’re designed for rough field screening, not health decisions.

Certified lab testing uses ICP-MS (inductively coupled plasma mass spectrometry), which can reliably measure arsenic down to 1 ppb or lower. That’s the resolution you need. A certified lab will also tell you exactly what your number is, not just whether it’s above or below an imprecise threshold.

If your well is in a region with known arsenic in groundwater, skip the strip entirely. Go straight to a lab.

How to Find a Certified Lab

The EPA maintains a list of certified drinking water laboratories for every state. You can find it at epa.gov’s certified lab locator. Search by state, and look for labs certified under the Safe Drinking Water Act. Your state health department’s environmental lab is usually on this list and is often the least expensive option.

For mail-in convenience, services like National Testing Laboratories and Tap Score ship you a sample collection kit, include a prepaid return envelope, and post results online within a week. They’re certified in multiple states and easy to use if your nearest lab is inconvenient.

When you contact a lab, ask specifically for a total arsenic or dissolved arsenic test by ICP-MS. Some labs offer an arsenic-only test for $15-30. Others include it in a full heavy metals panel or a comprehensive well water screen that runs $75-150. If you’ve never tested your well for anything, the broader panel is worth it. Arsenic rarely travels alone in problem groundwater.

Your state health department may also offer subsidized testing. Maine, New Hampshire, and New Mexico have run programs for private well owners. Availability varies by year and county funding. Call your state’s drinking water program and ask directly.

How to Collect the Sample Correctly

Certified labs send you their own sample container. Use it. Don’t substitute a bottle from home. Lab containers are pre-treated to preserve sample integrity, and using the wrong container can affect your results.

On collection day, run your tap for 2 minutes before filling the bottle. This clears standing water from pipes and fixtures, giving you a result that reflects what’s coming from the well. Some labs specify 5 minutes for older homes with longer pipe runs. Follow whatever your lab’s instructions say.

When you open the container, don’t touch the inside of the cap or the rim. Fill to the line marked on the bottle, close it firmly, and label it with your name and collection date.

Mail the sample the same day you collect it. Arsenic samples are typically stable for 14 days if the lab has pre-acidified the container, which most certified labs do as a standard step. Still, same-day or next-day mailing avoids any complications.

Store the sample at 4°C (a standard refrigerator temperature) if you can’t mail it immediately.

Understanding Your Results

When your report arrives, find the arsenic row and look at two things: the detected concentration and the unit (it should be ppb or micrograms per liter, which are the same thing).

Below 10 ppb means you’re within the EPA’s MCL for public water. For a private well, there’s no legal requirement to act, but it’s worth knowing the MCLG for arsenic is zero. The EPA set the MCL at 10 ppb because that’s achievable with current treatment technology, not because 10 ppb is harmless. Long-term exposure below 10 ppb still carries some increased cancer risk according to EPA’s own risk assessment. What you do with that information is your call.

Between 10 and 50 ppb, treatment is warranted. Reverse osmosis and activated alumina both reduce arsenic to below detectable limits in most cases. Don’t wait on this range.

Above 50 ppb is urgent. Consider using bottled water for drinking and cooking immediately while you arrange treatment. Consult a licensed water treatment professional for system selection.

What to Do If You Find Arsenic

If your test comes back above the limit, the arsenic contaminant page covers what you’re dealing with and where it comes from. The arsenic removal options page walks through treatment technologies in detail.

For broader well testing context, including what else to test for and how often, see the well water testing guide.

If you want help picking a mail-in lab service, the best mail-in water tests page compares the major options.

Sources

EPA, “Basic Information about Arsenic in Drinking Water”: epa.gov/ground-water-and-drinking-water/basic-information-about-arsenic-drinking-water
EPA, “Certified Laboratory Locator for Drinking Water”: epa.gov/dwlabcert
USGS, “Arsenic and Drinking Water from Private Wells”: usgs.gov
EPA, “National Primary Drinking Water Regulations, Arsenic”: epa.gov/ground-water-and-drinking-water/national-primary-drinking-water-regulations

Health disclaimer: This page provides general information about arsenic testing in private wells. It is not medical advice. Private well owners are responsible for their own water quality monitoring. If you have symptoms you associate with arsenic exposure, contact your doctor. For treatment decisions, consult a certified water treatment professional.