Arsenic in Well Water: Health Risks, Testing, and How to Remove It

Arsenic has no smell, no taste and no color, so the number on a lab report is the only way to know it is in your well. Home buyers call me reading it straight off an inspection report, 0.0213 or 19.2, and ask whether that is bad. The EPA limit is 10 parts per billion (ppb). On my customers' lab reports that shows up as 0.010 mg/L. Over 10, stop drinking the water and treat it. Under 5, you are under even the 5 ppb limit that New Jersey and New Hampshire set. Multiply mg/L by 1,000 to get ppb: 0.0213 mg/L is 21.3 ppb.

What your arsenic number means

At 10 ppb (0.010 mg/L) or more, drink and cook with other water and put in treatment. Between 5 and 10, you are over the 5 ppb limit New Jersey and New Hampshire set. My customers' lab reports print arsenic in mg/L, the same as ppm.

A home buyer once asked me whether there was a world where arsenic is not treatable. It is treatable. What changes from well to well is the equipment that has to go ahead of the arsenic tank, and the pH, iron and hardness on the report decide that.

What to do until the water is treated

Until the treatment is in, drink and cook with bottled water. New Jersey and Vermont both say so for a well over their limit.

• Do not boil it. Boiling does not take arsenic out. Minnesota and Oregon say it can raise the level as the water boils off.
• Showers, baths and laundry are fine under 500 ppb. Massachusetts says arsenic is not absorbed through the skin and does not evaporate into the air. Oregon adds one condition: do not swallow the water.

Have an arsenic number?

Text me a photo of your report

Send the whole report, not just the arsenic line. The pH, iron and hardness on it decide what goes ahead of an arsenic tank, or whether you need one at all.

Text Aidan443-277-2204 Call800-460-5810Aidan

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What arsenic does to your health

Arsenic is a known cause of cancer in people, and the risk comes from drinking it for years. The EPA links long-term drinking water over the limit to cancer of the bladder, lungs, skin, kidney and liver, and the World Health Organization adds diabetes and heart disease. Washington's health department notes the cancers can take decades to show up.

Most of the time there is nothing to feel. Dartmouth's arsenic researchers say U.S. levels are usually too low to cause obvious symptoms or make you sick right away. The first signs of long exposure show on the skin: darker patches, and small corns or hard patches on the palms and soles. The World Health Organization says those appear after about five years at high levels. If your family has been drinking the water for years, tell your doctor what the test showed.

How common arsenic is in well water

Of 336 well tests my customers ran from May to September 2026, 10 came back at 10 ppb or more and 23 at 5 or more. In 245 of them the lab found none above its reporting limit, and the highest was 33.8 ppb.

Nationally, the U.S. Geological Survey estimates about 2.1 million people on private wells drink water over 10 ppb, out of about 44 million people on wells. The odds run higher in much of the West and in parts of the Northeast and Midwest. New Hampshire estimates 25 to 30 percent of its private wells are at 5 ppb or more, and Minnesota puts about 10 percent of its wells over 10. Your state's odds do not tell you your own number; only the test does. The state-by-state picture is in arsenic in well water by state.

How to test your well for arsenic

Only a certified lab test gives you the number, and the pH, iron and hardness on the same report decide which system works. The well water test kit we sell ($199) reports 53 contaminants and water-chemistry values from one sample, run at an accredited lab, with arsenic measured by EPA method 200.8. On my customers' reports the lab's reporting limit for arsenic ran from 0.5 to 2 ppb, well under the 5 ppb ceiling Dartmouth tells well owners to ask for. Results usually arrive 2 to 4 weeks after you order.

If you only want the arsenic number, a state-certified lab can run arsenic by itself; Massachusetts puts that at $15 to $30. If the house already has treatment equipment, take the sample from a tap ahead of it so the lab sees the raw well water. Once treatment is in, test the treated water again: Dartmouth says right after the install, every few months until you know the system, then once a year. If you already have a report, how to read your well water test results walks through every line.

Which kind of arsenic your well has

The total arsenic on your report can be two forms added together: arsenic V, which treatment removes well, and arsenic III, which is much harder to remove. Arsenic III has to be oxidized into arsenic V before equipment can catch it.

ResinTech, the company that makes the resin in the arsenic tank we sell, says the resin removes only modest amounts of arsenic III. Its rule: when arsenic III is more than a quarter of the total, or 5 ppb or more, chlorinate the water ahead of the resin, then take the chlorine back out before the water reaches it. The well water test reports total arsenic only. The arsenic speciation test ($519) splits it into arsenic III and arsenic V, so you know whether that extra step belongs in your line before you buy anything.

What removes arsenic from well water

For every tap in the house, a tank of arsenic resin. For drinking water only, an under-sink reverse osmosis unit certified to NSF/ANSI 58 for arsenic.

If only the drinking water worries you, a certified under-sink reverse osmosis unit is a real option. Its NSF/ANSI 58 arsenic claim covers arsenic V only, and only for water that carries chlorine or has been shown to hold arsenic V alone, so the speciation test matters more on this path. When a home buyer in Alaska at 29 ppb told me there was already an RO under his kitchen sink, I told him that would do for now, but you don't get total reduction with it. Whatever you put in, have the water from that faucet tested after it is installed.

The case for whole house is every other tap: the bathroom sink, the ice maker, a guest who does not know. New Jersey recommends whole-house treatment above 5 ppb. New Hampshire recommends it at 100 ppb and up whenever someone might drink from an untreated tap. Minnesota's health department says water softeners and activated carbon filters alone will not remove arsenic.

The whole-house arsenic system we sell

The one arsenic system we sell is the Whole House Arsenic Removal System, $3,495 with free shipping to the lower 48. It is a 12 by 54 inch black Vortech tank with a Clack C1190 in/out head, the bypass already mounted, and 2 cubic feet of ResinTech ASM-10-HP arsenic-selective resin. The resin just absorbs the arsenic. The system never backwashes, so it needs no drain, no salt and no outlet, and it handles up to 10 gallons a minute. It brings arsenic V under the 10 ppb limit, and a lab test of the treated water once a year shows it still does.

The tank ships empty. The resin comes in two 1 cubic foot boxes and is loaded at install through the fill funnel that comes with it. We recommend a licensed plumber, who typically has it in within 1 to 2 hours, and I am on the phone at 800-460-5810 if your plumber has a question.

The resin wants clean water ahead of it. Our system page asks for iron under 0.3 ppm and manganese under 0.05 ppm, and soft water if yours is hard. As I told one buyer, if there's hardness in the water, that has to be treated before it can go through the arsenic tank. pH matters too. A customer in Maine whose well ran as high as pH 9.2 emailed to ask what that does to the resin. ResinTech rates it for pH 4 to 8, says it works best below 8, and says its capacity drops faster and faster as the pH rises.

Upkeep is the yearly test. When arsenic starts coming through, the tank is rebedded with two new boxes of ASM-10-HP resin at $945 each; the tank, head and bypass stay. Our system page puts that at typically 1 to 5 years. ResinTech lists this resin as having no arsenic dumping: run past the end of its life, the treated water does not go above what the well puts in. The system and its resin are on our arsenic filters page.

Where the arsenic tank goes

The arsenic tank goes after everything that treats pH, iron and hardness. Massachusetts says iron and manganese have to come out before arsenic treatment, and when a buyer asked me where the arsenic system would go, my answer was that it goes last, after what's already there.

The long version, with the reasons for each step, is in the correct order of well water treatment systems.

Frequently asked questions