Why Testing for Arsenic Matters

Arsenic is a naturally occurring element released into groundwater when bedrock and soil sediments slowly dissolve. It is most common in private wells in New England, the Mid-Atlantic, the Upper Midwest, and parts of the West and Southwest (see arsenic risk by state for a state-level breakdown). According to the U.S. Geological Survey, an estimated 2 million Americans on private wells drink water exceeding the EPA arsenic limit, and most have no idea.

The reason most people miss it is simple: arsenic is invisible. It has no taste, no smell, and no color. Unlike iron (orange staining) or sulfur (rotten egg smell) or low pH (blue-green stains), there is no household symptom that tells you arsenic is present. The only path to knowing is a test.

The health side is serious. The International Agency for Research on Cancer classifies arsenic as a Group 1 human carcinogen. The CDC ties long-term exposure to bladder, lung, and skin cancers, plus cardiovascular and developmental effects. See our complete guide to arsenic in well water for a full breakdown of health risks and where arsenic comes from. The EPA set the federal Maximum Contaminant Level (MCL) at 10 parts per billion in 2006, lowered from 50 ppb. New Jersey and New Hampshire enforce a stricter 5 ppb standard. The World Health Organization guideline is also 10 ppb.

Three Ways to Test for Arsenic

You have three practical options for measuring arsenic in well water, ranked here from cheapest and least accurate to most accurate. The honest answer is that only one of them gives you a number you can act on. The other two have a place, but read this section carefully before you spend the money.

Method 1: At-Home Arsenic Strip Kits

Hardware-store and Amazon arsenic strip kits use a chemical reaction (typically zinc and an acid) to release arsine gas from any arsenic in the sample. The gas is captured on a treated test strip that turns yellow or brown. The deeper the color, the more arsenic.

Popular brands include SafeHome, Industrial Test Systems Quick Arsenic, Hach EZ Arsenic, and the Ascel kit. The procedure takes 10-30 minutes per sample and involves real chemistry (acids and zinc dust), so read the safety instructions before opening the kit.

What strip kits are good for

• A first-pass screen if you have never tested before and want to know whether arsenic is even on the radar
• Confirming the general presence of arsenic before paying for a full lab panel
• Testing multiple sources around a property (different wells, faucets pre and post any treatment)

What strip kits are not good for

• Reading near the EPA action level. Most consumer strip kits read in 10, 25, or 50 ppb increments. The EPA limit is 10 ppb. A strip that shows "10 ppb" on the chart could be 5 ppb or 25 ppb in reality. Not enough resolution to make a decision.
• Speciation. Strips report total arsenic only. They cannot tell you whether you have arsenite (As III) or arsenate (As V), and that matters for treatment.
• Defensible documentation. A real estate transaction, a mortgage condition, or a state-mandated record needs a certified lab result, not a strip color match.
• Sizing a treatment system. You also need pH, iron, silica, sulfate, and competing-ion data, and strip kits give you none of that.

The 2018 USGS study referenced earlier specifically warned that field strip kits can produce inconsistent readings depending on sediment in the sample, sample temperature, and even how vigorously the user shakes the bottle. Use them as a first look, not as the final answer.

Method 2: County or State Health Department Lab

Many states with known arsenic-prone geology offer subsidized or free arsenic testing for private well owners through cooperative extension offices, county health departments, or state environmental labs. The Minnesota Department of Health, New Hampshire Department of Environmental Services, Maine Center for Disease Control, New Jersey Department of Environmental Protection, and Wisconsin DNR all run programs of this kind.

How to find your state's program

1. Search "[your state] private well arsenic testing program"
2. Check your state's Department of Health or Department of Environmental Protection website for a list of certified labs
3. Call your county health department directly. Even if they do not run testing themselves, they usually know who does
4. If you are buying a home, ask the lender or title company if they have a recommended local lab. Mortgage-driven testing usually goes through the same regional labs

What state lab programs are good for

• Cost. Often free or under $50
• Trusted regulatory result. Defensible for permits and real estate
• Local context. State labs often know which counties have known arsenic hot spots and can flag your result accordingly

The catch

Turnaround is variable. Some state programs return results in two weeks; others take six. Most state programs only test for total arsenic, not the species breakdown. And if you want a complete water chemistry panel (arsenic plus pH, iron, hardness, alkalinity, silica) you usually have to pay for each parameter separately, which adds up fast. State programs work best when arsenic is the one specific question you need answered.

Method 3: Certified Independent Lab Test (Recommended)

A certified independent lab test is the gold standard for arsenic. You collect a sample at home, ship it overnight, and get a full report back in 5-10 business days. NELAC (National Environmental Laboratory Accreditation Conference) and ELAP (Environmental Laboratory Approval Program) labs detect total arsenic down to 1 ppb, well below the EPA action level. Most can run speciation as an add-on if you ask up front.

Our Well Water Test Kit is $199 and works as a complete arsenic test kit (total arsenic plus 52 other contaminants in one panel). It uses the SimpleLab network of NELAC and ELAP certified labs, the same network TapScore uses, with arsenic detection to 1 ppb. The kit ships with acid-preserved sample bottles, instructions, and prepaid overnight return shipping. Aidan personally reviews the results before any treatment recommendation, and there is no obligation to buy a system after the test. You can also browse our arsenic and full-panel water test kits to compare options.

If you only need an arsenic-only test (no other parameters), single-analyte tests from labs like TapScore and Aqua Test Labs run $40-90. The downside is you only get one number. Treating a positive arsenic result requires knowing your pH, iron, silica, and a few other parameters anyway, so most homeowners save money long-term by ordering the full panel up front. For a side-by-side comparison of the major lab kits, see our best well water test kit guide.

How to Collect a Proper Arsenic Sample

A bad sample produces a bad number. Arsenic samples have a few specific requirements that other contaminants do not, and getting them wrong can give you a falsely low or falsely high reading.

Step by step

1. Use the bottle the lab sent. Arsenic sample bottles are usually preserved with a small amount of nitric acid to keep dissolved arsenic from sticking to the bottle walls or oxidizing during shipment. Do not rinse this acid out, do not transfer the sample to a different container, and do not over-fill past the marked line.
2. Sample from before any treatment. The point of an arsenic test is to know what is in the well, not what your existing equipment is removing. Sample from an outdoor spigot or the faucet closest to where the water enters the house, before any softener, filter, or RO system. If the only access is post-treatment, label it clearly so the lab knows.
3. Run cold water for 3-5 minutes to flush out anything sitting in the pipes overnight. You want a representative sample of fresh well water, not water that has had hours to interact with copper or galvanized plumbing.
4. Remove any aerator or screen from the faucet before sampling. Aerators can trap iron and biofilm that throws the result.
5. Reduce flow to a slow steady stream. Splashing introduces air and can shift the arsenic species (oxidizing As III to As V) before the sample is even sealed.
6. Fill, cap, and refrigerate immediately. Get the sample to overnight shipping the same day. Heat and time both degrade the integrity of an arsenic sample.

If your well has visible iron or you are seeing orange staining at fixtures, mention it on the chain-of-custody form. High iron interferes with some arsenic analytical methods, and the lab may use a different method to compensate.

What Your Arsenic Number Means (in ppb)

Arsenic in drinking water is reported in parts per billion (ppb), sometimes written as micrograms per liter (mcg/L or µg/L). They are the same unit. The EPA Maximum Contaminant Level is 10 ppb. New Jersey and New Hampshire enforce 5 ppb. Below is the practical scale most water-treatment professionals use when interpreting a result for a homeowner.

Why Speciation Matters: As(III) vs As(V)

"Total arsenic" is what most labs report by default, but arsenic in groundwater shows up in two main forms (called species or oxidation states) and they behave very differently in a treatment system:

• Arsenate, As(V). The oxidized form. Carries a negative charge. Removed efficiently by ion-exchange resin, activated alumina, and iron-based adsorbents. This is the easy one.
• Arsenite, As(III). The reduced form. Carries no charge in typical drinking-water pH ranges. Slips right past most arsenic media unless you oxidize it to As(V) first using chlorine, ozone, or a manganese-greensand pre-filter.

If your raw water sits in an oxygen-poor aquifer (deep wells, anaerobic groundwater), expect a higher fraction of As(III). If it has been exposed to oxygen (shallow wells, water that has sat in a pressure tank), more of it will be As(V). Many wells are a mix.

Practically: if your test reports total arsenic over 10 ppb and you do not know the species, either ask the lab to run speciation, or add a pre-oxidation step to be safe. A simple chlorine injection ahead of the arsenic tank converts almost all As(III) to As(V), guaranteeing the system works regardless of the incoming species mix. If that sounds confusing, that is what the phone call is for. Send the result to 800-460-5810 and Aidan will tell you whether you need speciation or pre-oxidation in about 5 minutes.

The Other Parameters You Need for Sizing

Arsenic in isolation does not size a system. To order the right tank and the right media, the lab also needs to report a few competing parameters. This is where the cheap arsenic-only tests stop being a bargain. The 5 numbers we look at alongside arsenic on every job:

This is also why we point homeowners to a full panel even if arsenic is the only initial concern. Three months later, when your test shows arsenic at 22 ppb, you do not want to send a second sample to find out your silica is 45 ppm. The $199 panel reports all of this at once. For a deep dive on interpreting the rest of the report, see our how to read your well water test results guide.

Paraphrased from a recent customer call. Iron, hardness, and arsenic almost always travel together on Mid-Atlantic and Upper-Midwest wells. The treatment chain (iron filter, then softener, then arsenic system) is the standard approach when all three show up on a test, and it is exactly why we push the full lab panel before any equipment goes in.

5 Common Arsenic Testing Mistakes

1. Trusting a strip kit at the EPA action level

Most consumer arsenic strip kits read in 10 or 25 ppb increments. The EPA limit is 10 ppb. A strip showing the "10" color block could be 5 ppb or 20 ppb, and the difference matters. Strip kits are a screen, not a measurement. If the strip shows any arsenic at all, send a sample to a certified lab.

2. Sampling from an outdoor hose or after a softener

Outdoor hoses can leach lead and zinc from old fittings, contaminating the sample. Sampling after a water softener gives you the post-treatment number, not the well water number. Always sample from the cold tap closest to the well, before any treatment, with the aerator removed.

3. Forgetting to ask for speciation

If your water is from a deep, oxygen-poor aquifer, a meaningful fraction may be As(III) arsenite. A "total arsenic" result alone tells you the level but not which form. Without speciation, you have to assume the worst case and add pre-oxidation. If you ask the lab up front, the As(III)/As(V) breakdown is usually a $25-75 add-on.

4. Skipping the full water chemistry panel

Arsenic does not exist in isolation. A 14 ppb arsenic result with iron at 1.5 ppm and silica at 35 ppm requires a different system than the same arsenic level with no iron and low silica. Pay once for a full panel; do not chase parameters one at a time.

5. Testing once and assuming it never changes

Arsenic levels can shift seasonally, after well work, after a drought, or after a heavy rainfall event that draws shallow groundwater into the well. Retest every year, after any pump or well repair, and after any major change in your water (taste, color, pressure, anything).

What to Do at Each Arsenic Level

Frequently Asked Questions

Written by Aidan Walsh, owner of Mid Atlantic Water. 32+ years installing well water treatment systems across Pennsylvania, Maryland, Delaware, New Jersey, Virginia, and beyond. Article reviewed April 2026.