Nothing will tell you it is there
Every other problem in this cluster announces itself. Iron stains the laundry.
Sulfur smells. Hardness leaves scale on the kettle. Acidic water turns the sink
blue-green.
Arsenic does none of that. It is colourless, tasteless and odourless at every
concentration that matters. There is no glass test, no smell test, no visible
symptom. The only way to know is to send a sample to a lab.
That is the whole argument for this page.
How common is it
Minnesota Department of Health: “About 10 percent of Minnesota’s private wells
have arsenic levels higher than 10 µg/L.”
One in ten. That is a Minnesota figure and it reflects Minnesota geology —
arsenic “occurs naturally in rocks and soil… and can dissolve into
groundwater,” so prevalence tracks bedrock rather than state lines and the
number does not transfer elsewhere.
What it does establish is that arsenic in private wells is common where the
geology favours it, not a rare event.
The limit, and who it applies to
EPA allows a maximum of 10 micrograms per litre in community water
systems.
Your well is not a community water system. Nobody tests it against that number,
nobody reports on it, and nothing changes if it is exceeded. The standard is
the right benchmark for reading your own result — it just does not come with
anyone enforcing it.
Why it matters at low levels
Minnesota Health is specific: “Consuming water with even low levels of arsenic
over a long time is associated with diabetes and increased risk of cancers of
the bladder, lungs, liver, and other organs.”
Also associated: cardiovascular and respiratory disease, reduced intelligence in
children, and skin problems.
Note the framing — low levels over a long time. This is a cumulative exposure
problem, not an acute one. There is no moment at which the water tastes wrong
and you stop drinking it.
Testing
Minnesota Health’s guidance is modest: “Test your well for arsenic at least
one time beyond the initial well water test when the well is first
constructed.”
Once, deliberately, is most of the value. Arsenic comes from the rock the water
moves through, so unlike bacteria it does not spike after heavy rain or vary
with a failed well cap. A clean result on a stable aquifer stays informative.
Treatment
Minnesota Health lists seven methods that reduce arsenic:
- Reverse osmosis
- Distillation
- Adsorptive media
- Anion exchange
- Ozonation and filtration
- Oxidation filtration
- Chlorination and filtration
We are not ranking these by removal efficiency, and you should be careful of
anyone who does casually. Arsenic occurs in more than one chemical form, and
how well a given technology performs depends on which form is present. A
removal percentage quoted without naming the species it applies to is not a
usable number.
If a supplier quotes you one, the question to ask is: which form of arsenic,
and how do you know which one is in my water?
Where point-of-use treatment sits relative to the rest of the system is worked
through in the sizing method. The rest of the cluster starts
at well water treatment.
The bottom line
Test for arsenic deliberately, because nothing about your water will reveal it — no colour, no taste, no smell at any concentration that matters. Once is most of the value, since arsenic comes from bedrock rather than seasonal contamination. Compare your result against EPA's 10 micrograms per litre, remembering that limit binds public systems and not your well. Treatment exists in several forms, but effectiveness depends on which chemical species is present, so ask any supplier which form their removal figure applies to and how they know which one you have.
Who this is not for
This page does not rank treatment methods by removal efficiency, because efficiency depends on which chemical form the arsenic is in, and we could not verify those figures at source. Anyone quoting you a removal percentage should be asked which arsenic species it applies to. It also uses Minnesota prevalence data, which reflects Minnesota geology and does not transfer.
Questions
Can you taste or smell arsenic in well water?
No. Arsenic is colourless, tasteless and odourless. Every other common well problem announces itself — iron stains, sulfur smells, hard water leaves scale. Arsenic gives no sensory signal at any concentration, which is why it has to be tested for deliberately rather than noticed.
What is the arsenic limit in drinking water?
EPA allows a maximum of 10 micrograms per litre in community water systems. That standard does not apply to private wells — no one monitors a private well against it. The number remains the right benchmark for judging your own test result.
How often should I test my well for arsenic?
Minnesota Department of Health advises testing at least one time beyond the initial test done when the well was constructed. Arsenic comes from the rock the water moves through, so unlike bacteria it does not fluctuate with weather or seasonal contamination events.
What removes arsenic from well water?
Minnesota Health lists reverse osmosis, distillation, adsorptive media, anion exchange, ozonation and filtration, oxidation filtration, and chlorination and filtration. Which performs best depends on the chemical form the arsenic is in, so test results should precede equipment choice.
Sources — 8 claims
- EPA — National Primary Drinking Water Regulations
EPA's Maximum Contaminant Level for arsenic is 0.010 mg/L. It is a legally enforceable standard. (captured 2026-09-09)
Limits: A legally enforceable federal health standard for public water systems. It does not apply to private wells, which are unregulated — the number is still the right reference point, but no one is testing a private well on the homeowner's behalf. - Minnesota Department of Health — Arsenic in Well Water (page dated 2025-08-01)
The maximum level of arsenic EPA allows in community water systems is 10 micrograms per litre. (captured 2026-09-09)
Limits: Applies to community water systems. A private well is not covered, monitored or reported on by anyone. - Minnesota Department of Health — Arsenic in Well Water (page dated 2025-08-01)
Consuming water with even low levels of arsenic over a long time is associated with diabetes and increased risk of cancers of the bladder, lungs, liver and other organs. (captured 2026-09-09) - Minnesota Department of Health — Arsenic in Well Water (page dated 2025-08-01)
Minnesota Department of Health also associates arsenic exposure with cardiovascular and respiratory disease, reduced intelligence in children, and skin problems. (captured 2026-09-09) - Minnesota Department of Health — Arsenic in Well Water (page dated 2025-08-01)
Arsenic occurs naturally in rocks and soil and can dissolve into groundwater. (captured 2026-09-09) - Minnesota Department of Health — Arsenic in Well Water (page dated 2025-08-01)
About 10 percent of Minnesota's private wells have arsenic levels higher than 10 micrograms per litre. (captured 2026-09-09)
Limits: A Minnesota figure. Arsenic is geology-driven, so it does not transfer to other states — it establishes that the problem is common where geology favours it, not a national rate. - Minnesota Department of Health — Arsenic in Well Water (page dated 2025-08-01)
Minnesota Department of Health advises testing a well for arsenic at least one time beyond the initial test performed when the well is constructed. (captured 2026-09-09) - Minnesota Department of Health — Arsenic in Well Water (page dated 2025-08-01)
Treatment methods that reduce arsenic include reverse osmosis, distillation, adsorptive media, anion exchange, ozonation and filtration, oxidation filtration, and chlorination and filtration. (captured 2026-09-09)
Limits: A list of methods that reduce arsenic. It does not state removal efficiency for any of them, and efficiency depends on the arsenic species present.
