Arsenic filters are a narrow category, because most household filtration does nothing at all for arsenic. Carbon does not remove it, sediment cartridges do not remove it, and a softener does not remove it. What works is reverse osmosis, adsorptive media designed for arsenic, or anion exchange, and which of those performs depends on the chemical form the arsenic is in when it reaches the filter.
Two forms, two very different results
Arsenic occurs naturally in rock and dissolves into groundwater in two oxidation states. The oxidized form is captured well by every one of the technologies below. The reduced form, which is common in oxygen-poor well water, passes through most of them and is the single biggest reason a correctly chosen filter underperforms in the field. The practical consequence is that many arsenic systems include an oxidation step in front of the removal media, converting the arsenic into the form the media can hold. A lab test that reports both forms is worth paying for, since it changes the design.
Reverse osmosis at the point of use
A reverse osmosis membrane rejects arsenic effectively and is the most common household answer, installed under the kitchen sink to treat drinking and cooking water only. That scope is deliberate: arsenic is an ingestion concern rather than a skin contact one, so treating showers and laundry adds cost without adding protection. The membrane needs protecting in turn, with sediment and carbon pre-filters, and with iron removal and softening ahead of it on a difficult well. Choose a model whose certification explicitly lists arsenic reduction, and confirm which form of arsenic that listing was tested against.
Adsorptive media and anion exchange
Adsorptive media tanks use iron-based or activated alumina media that binds arsenic as water flows through, and they are the usual choice when a whole house needs treating or where a point of use unit is impractical. The media has a finite capacity, exhausts silently and must be replaced on a schedule based on your measured water chemistry and usage rather than on a generic interval. Anion exchange works in a similar tank format and is effective on the oxidized form, but it is sensitive to competing ions such as sulfate, which can displace captured arsenic and release a slug of it.
What you must not rely on
Boiling concentrates arsenic rather than removing it. Carbon block and granular carbon cartridges are not arsenic filters and their taste and odor performance says nothing about it. Ion exchange softeners remove hardness, not arsenic. Ultraviolet lamps disinfect and do nothing to dissolved metals. Pitcher filters are not arsenic filters unless a specific model is certified for it, and most are not. If a product does not name arsenic in its certified reduction list, assume it does not remove arsenic, however good it is at the job it was designed for.
Testing and confirming the filter still works
Arsenic is colorless, tasteless and odorless, so there is no household symptom to watch. The EPA notes that private wells are not federally regulated under the Safe Drinking Water Act, and that a USGS study of 2,100 private wells found about one in five carried at least one contaminant above a human-health benchmark. Test the raw water before choosing equipment, and test the treated water afterward on a regular cycle, because adsorptive media reaching exhaustion produces no warning. Our replacement water filters guide covers keeping cartridge and media changes on a schedule you actually follow.
Questions people ask about arsenic filters
Does a whole house carbon filter remove arsenic?
No. Carbon handles chlorine, taste, odor and many organic compounds, and has essentially no effect on dissolved arsenic. Removal needs reverse osmosis, arsenic-specific adsorptive media or anion exchange.
Do I need to treat the whole house for arsenic?
Usually not. Arsenic is an ingestion risk rather than a skin contact one, so most households treat the kitchen tap for drinking and cooking water and leave showering and laundry on untreated supply.
Why did my arsenic filter stop working?
Two common reasons: the media reached its capacity and exhausted without any visible sign, or the arsenic in your water is in the reduced form that most media do not capture, so it needs oxidizing first.
Is bottled water a reasonable substitute?
It solves drinking water in the short term while you arrange testing and equipment, but it is an expensive permanent answer for a household and it does nothing about cooking water unless you use it for that too.