Quick Answer: Most families with arsenic in a private well get the most protection per dollar from a certified reverse osmosis system at the kitchen sink. The Waterdrop G3P800 carries NSF/ANSI 42/53/58 certification, and its performance data sheet lists arsenic reduction. If you want every tap treated, a whole-house media tank built on ResinTech's arsenic resin, like the ASM-10-HP system, works on arsenic V. If your lab report shows arsenic III, you need an oxidation step in front of it.
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Ten parts per billion. That's the EPA's enforceable limit for arsenic in public drinking water (0.010 mg/L). Private wells aren't covered by that rule, so nobody will tell you when yours goes over. If your lab report came back at 12, 30 or 80 ppb, you already know more than most of your neighbors. The next step is choosing a filter that matches the kind of arsenic you have, which most product pages skip.
In this guide
The question nobody asks: arsenic III or arsenic V?
Arsenic in groundwater comes in two common forms, and filters treat them differently. ResinTech, which makes the ASM-10-HP media used in two of our picks, is direct about it: the resin targets arsenate (As V), and arsenite (As III) is not removed directly. It needs upstream oxidation first, such as chlorination or aeration.
So if your lab only reported "total arsenic," call them back and ask for speciation, or retest with a lab that offers it. Our guide on how to test well water for arsenic covers what to request. The answer changes what you buy:
- Mostly As V → adsorptive media (whole house) or RO (one tap) can work as-is.
- Significant As III → add an oxidizing step ahead of whole-house media, or confirm your RO's performance data covers your situation. If you're unsure, get the seller to confirm in writing.
Whole house, or just the water you drink?
This is the biggest money decision, so here's our opinion. For most homes, start with the water you drink and cook with. The EPA's arsenic limit is a drinking-water standard, so that's where treatment counts first. A point-of-use RO at the kitchen sink is cheaper to buy, cheaper to run, and easier to verify.
Whole-house arsenic treatment makes sense if your levels are very high, if you want every tap safe (kids drinking from the bathroom sink, guests, an outdoor spigot used for drinking), or if local guidance recommends it. Your report will also matter, since iron, sulfate, silica and pH all affect how whole-house media performs. If you need help reading it, see how to read a full well water lab report.
Whole-house options
ASM-10-HP arsenic system (1 cu ft)
A whole-house tank holding one cubic foot of ResinTech ASM-10-HP: a strong-base hybrid anion resin with hydrated iron oxide spread through the beads. Per ResinTech's published data:
- Reduces arsenate (As V) from 50 ppb to under 10 ppb.
- Rated for 500,000+ gallons per cubic foot under that 50 ppb test condition.
- Recommended flow is 1 to 5 gpm per cubic foot, so a one-cubic-foot tank tops out around 5 gpm.
- Works in a pH range of 4 to 8. Capacity drops above pH 8.
- High silica, high sulfate, suspended solids and on-off use all cut its capacity.
- Not regenerated in residential use. Regenerating arsenic-loaded media creates a hazardous brine problem, so you replace the media when it's spent.
Our take: a sound design if your arsenic is mostly As V and your pH is under 8. At 5 gpm, it's sized for a modest household. Large homes with high peak flow would need a bigger tank. If your pH runs high, check interpreting pH and hardness together before buying.
Crystal Quest 4–6 GPM whole house arsenic filter
A packaged multi-stage whole-house system with a stand, using what Crystal Quest calls arsenic oxide multistage media, rated at 4–6 gpm for the main water line. On its arsenic page, Crystal Quest describes its arsenic media as a strongly basic hybrid anion exchange resin designed to selectively remove arsenic, and says performance is barely affected by chloride, bicarbonate and sulfate.
Good fit: homeowners who want a complete, pre-configured system rather than a tank-and-media setup.
What we couldn't confirm: Crystal Quest's page doesn't say how this system handles As III versus As V, and it doesn't list a warranty or pretreatment requirements. Ask before you order, especially if your lab shows As III.
AFWFilters activated alumina cartridge: only if fluoride is also a problem
This is a 4.5" × 20" cartridge packed with activated alumina (synthetic aluminum oxide) that drops into a standard 20" Big Blue-size housing. AFWFilters describes the media as specially prepared for fluoride reduction and highly selective for fluoride, arsenic and lead. Like all activated alumina, it works best at lower pH, and the listing ties maximum removal efficiency to the treated water's pH, so test pH before you buy.
Our honest call: activated alumina needs slow flow and long contact time, and a single cartridge holds far less media than a backwashing tank. Treat it as a low-flow stage for a dedicated drinking-water line, or a pick for homes with both fluoride and arsenic problems, not a whole-house arsenic system. The listing doesn't give a rated flow, a capacity in gallons, or say which arsenic form it targets. For well water above 5 ppb arsenic, test after installation and replace the cartridge on a schedule based on those results.
Drinking-water options
Waterdrop G3P800 tankless RO
An 800 GPD tankless under-sink RO, certified by IAPMO to NSF/ANSI 42, 53 and 58, plus 372 for lead-free materials. Waterdrop's performance data sheet lists arsenic at 0.1151 ppm in and under 0.0005 ppm out (over 99% reduction), alongside fluoride, nitrate and several heavy metals.
Who it's for: most well owners with arsenic who want safe drinking and cooking water from one tap.
Worth knowing: one independent reviewer didn't find arsenic on the certification lists they checked. Before you rely on it, look up the model in IAPMO's listing and confirm arsenic is covered for your level. The listing we link is a bundle with a spare RO filter, and one reviewer reports membrane life of about two years. A claimed 3:1 pure-to-drain ratio measured closer to 2.2:1 in that independent test.
IPW Aries Arsenic Removal Cartridge (AF-10-3695)
A cartridge filled with the same ResinTech ASM-10-HP media, in a slim 10-inch size that fits standard residential housings. A Canadian dealer lists it at 25 microns nominal, up to 125 psi and 100°F, made in the USA.
Who it's for: a dedicated drinking-water line, or an add-on stage, if you already have a 10-inch housing and your arsenic is As V.
The limits: we found no certification and no gallon rating published for this cartridge. Because the media is ASM-10-HP, the same As III caveat applies: it won't remove arsenite without oxidation upstream. Retest after installing it rather than assuming it works.
A worked example
Here's a typical case. A family of four's lab report shows 35 ppb total arsenic, speciated as mostly As V, with pH 7.4, low iron, and nothing else unusual.
- Drinking water only: an RO at the kitchen sink is the obvious first step. It's the least expensive route, and the result is easy to verify with a single post-install test.
- Whole house: the ASM-10-HP tank fits this water well. The pH is inside ResinTech's 4–8 range and the arsenic is the form the resin targets. But at about 5 gpm for one cubic foot, a four-person household with two bathrooms running at once could outrun it. They'd want a larger tank, or to keep the whole-house unit as a backstop and still use RO for drinking water.
Now change one number: the pH comes back at 8.4. ResinTech says capacity drops above 8, and activated alumina also loses efficiency as pH rises. The RO becomes the clear choice, and anyone still wanting whole-house treatment should get a dealer to design around the pH.
Five questions for any arsenic system seller
- Which arsenic form does this media remove, As III, As V, or both?
- What's the maximum flow rate for this tank size?
- What pH range does it need, and what's mine telling you?
- How do silica, sulfate, phosphate or iron in my report affect capacity?
- When the media is spent, do I replace it or regenerate it, and how is it disposed of?
If a seller can't answer the first question, keep shopping.
Where arsenic treatment sits in the line
Whole-house arsenic media generally goes after sediment and iron treatment, so particles and iron don't use up its capacity. If you have As III, the oxidation step goes before it. A point-of-use RO comes last, at the tap. Our well water treatment train order guide shows the whole sequence for a well with several problems.
The part people skip: retesting
Arsenic media doesn't change color or smell when it's spent, so the only way to know it's still working is to test treated water. Test it a few weeks after install, then on a regular schedule after that. See how often to test well water for a schedule by contaminant. When media is spent, ResinTech's guidance is to replace it rather than regenerate it.
Quick answers
Does a water softener remove arsenic? Don't count on it. None of the softener listings we've reviewed for this site makes an arsenic claim. Arsenic needs a dedicated method.
What do I do with spent arsenic media? ResinTech says to replace spent media rather than regenerate it at home. Ask your local waste authority how they want it handled before you bag it up.
How do I know the RO is still working? Test the RO water, not the raw water, on a schedule. Change the membrane when the manufacturer says to, or sooner if a test shows arsenic coming through.