Best Arsenic Water Filter for Well Water (Whole House vs Point of Use) | 2026 Buyer's Guide

The best arsenic water filter for a well depends on which taps you need to protect. For every tap in the house, it is a whole-house tank of resin made to catch arsenic. If the kitchen faucet is your only drinking water, an under-sink reverse osmosis unit certified to NSF/ANSI 58 for arsenic treats that faucet, and Dartmouth's arsenic researchers call that a good option below 250 ppb. Either way, a lab test of the treated water is what proves it works.

Read the whole lab report before you buy either one. A caller in October had 13.1 ppb arsenic and 1.36 ppm iron and asked what else he should have. Arsenic attaches itself to iron, so I told him the iron filter he needed anyway would, if everything's right in the condition of the water, pull the arsenic out with the iron: "I would try that first and retest it after you put that in, before spending a bunch of money on an arsenic filter."

Which arsenic filter fits your well

If anyone drinks from taps other than the kitchen faucet, treat the whole house. If the kitchen faucet is your only drinking water and the arsenic is under 250 ppb, a certified under-sink unit is a good option. Oregon's health authority puts it plainly: a unit at one tap does not protect anyone drinking from the others.

Have your lab report?

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Send the whole report, not just the arsenic line. The iron, hardness and pH on it decide which filter fits your well, or whether you need one at all.

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Arsenic filters compared side by side

Every filter on this list that works removes the easier kind of arsenic. They differ in which taps they treat, how much of the harder kind they catch, and the upkeep. Minnesota's health department lists reverse osmosis, distillation, adsorptive media, anion exchange and oxidation filtration as the treatment units that reduce arsenic, and Oregon says reverse osmosis is the one used most.

Sources for the table: ResinTech for the resin we use and for plain anion resin; Massachusetts for anion exchange, adsorptive media, reverse osmosis and cartridges; Minnesota and Dartmouth for softeners, carbon and boiling.

For every tap, the tank we sell uses ResinTech ASM-10-HP, an arsenic-selective resin with iron oxide spread through each bead. ResinTech lists it as having no arsenic dumping: unlike plain anion resin, a tank run past its end does not send out more arsenic than the well puts in.

For the kitchen faucet, under-sink reverse osmosis is a real option. When a couple who already had an arsenic tank asked me about adding one, I told them RO "removes things carbon can't remove, but it just doesn't produce a lot of water."

What certification to look for

Buy an under-sink reverse osmosis unit certified to NSF/ANSI 58 for arsenic. That certification covers only arsenic V, the easier kind. NSF's standard limits that claim to water that carries a chlorine residual or has been shown to hold only arsenic V. Dartmouth's researchers say to look the unit up on the NSF website, scroll down to arsenic, and choose one that brings arsenic to 5 ppb or lower.

Whole-house tanks are a different case. Minnesota tells well owners to choose a system certified by NSF, UL or WQA. On the whole-house system we sell, the certification is the resin's, not the tank's. ResinTech lists the resin as WQA Gold Seal certified for use in drinking water and as meeting NSF/ANSI/CAN 61, the standard for what materials that touch drinking water may add to it. NSF says that standard does not set performance requirements, so neither one rates how much arsenic a tank takes out.

For our tank, and for any filter, the proof is a lab test of the treated water. Dartmouth says to test it once the system is running and then every year; Oregon says to test the treated water at least once a year and the untreated well water at least every three years.

Fix the iron before the arsenic

Remove iron and manganese before the arsenic. An iron filter can take some arsenic out with the iron. That is why I told the caller in the opening to put the iron filter in first and retest. Minnesota counts oxidation filtration, the way an iron filter works, among the treatments that reduce arsenic.

Massachusetts says iron and manganese have to be removed before arsenic treatment. Our system page asks for iron under 0.3 ppm and manganese under 0.05 ppm, with a water softener ahead if the water is hard, and ResinTech rates the resin for pH 4 to 8. The arsenic tank goes after whatever treats pH, iron and hardness. The full order is in the correct order of well water treatment systems.

The harder kind of arsenic needs chlorine first

The harder kind, arsenic III, has to be changed into arsenic V before a filter can catch much of it. The total arsenic on a lab report can be the two forms added together. Massachusetts lists chlorine, hydrogen peroxide and ozone as what does it (they are called oxidants), with chlorine the easiest to get for a home.

ResinTech's rule for the resin in our tank: 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 the two forms, so you know whether that step belongs in your line before you buy anything. More on the two forms is in arsenic III and arsenic V.

What ships with our whole-house system

The one arsenic system we sell is the Whole House Arsenic Removal System, $4,795 with free shipping to the lower 48. It is two tanks. The first 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 resin. The second is a 1.5 cubic foot carbon tank on the same Clack head, because new arsenic resin can give the water a fishy smell and taste for a while, and the carbon takes that out before it reaches your taps. It needs no drain line, no salt and no electrical outlet. It handles up to 10 gallons a minute.

What ships: the arsenic tank with the head and bypass on it, the carbon tank with its head and a bypass valve, the resin in two 1 cubic foot boxes, 1.5 cubic feet of carbon in two boxes, and a fill funnel. Both tanks ship empty, and the media is loaded at install through the funnel.

I recommend having a plumber put it in. There is no drain line and no electricity, just an inlet and an outlet on each tank, so it is about an hour or two of a plumber's time per tank, and I'm a phone call away for your plumber at 800-460-5810. If you'd rather do it yourself, text me with any questions.

Upkeep is the yearly test of the treated water. 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. The carbon lasts about 4 to 5 years and is replaced in the same tank at $295 a cubic foot.

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