Water problem
Arsenic
A naturally occurring element in bedrock across parts of the Northeast. It dissolves into groundwater, so private wells in affected geology can carry it without any industrial source nearby.
What you might notice
- None that are detectable at the tap
- A drilled bedrock well in an area with known arsenic geology
- Neighbouring wells with positive results
A geological problem, not an industrial one
Arsenic in Northeast groundwater is usually natural. It occurs in bedrock and dissolves into water moving through fractures, which means a well can carry it with no industrial source anywhere nearby.
Because it follows geology, it is patchy at a very local scale. One property can have a significant concentration while a neighbour a few hundred feet away does not, depending on which fracture system each well draws from. Neighbourhood results are a useful prompt to test but not a substitute for testing.
It has no taste, no smell, and no colour, and the health concerns are associated with long-term exposure rather than immediate effects. There is nothing about drinking it that would alert you.
Ask for a speciated test
The federal limit is 10 micrograms per litre. A standard test reports total arsenic against that limit, which tells you whether you have a problem but not how to treat it.
Arsenic occurs in two forms. Arsenic V is removed effectively by reverse osmosis and by adsorptive media. Arsenic III is not, and passes through a membrane far more readily. It has to be oxidised to arsenic V first.
So the useful test is a speciated one that reports both. Specifying treatment from a total arsenic figure alone is how systems end up underperforming, and retrofitting an oxidation stage afterwards costs more than including it at the start.
How to respond to a result
Below the limit with no infant or pregnancy in the household, annual monitoring is proportionate. Arsenic concentrations in a given well tend to be reasonably stable, so a clean speciated result is genuinely informative.
Above the limit, point-of-use reverse osmosis at the kitchen tap is the most common residential response, because the exposure route that matters is drinking and cooking rather than bathing. Whole-house adsorptive media is used where treated water is wanted throughout.
Retest after any treatment is installed, and then annually. Media exhausts, and with a contaminant that gives no sensory warning the test is the only feedback the system provides.
How to confirm it
A laboratory test. The federal limit is 10 micrograms per litre. The test should distinguish arsenic III from arsenic V, because that determines the treatment. Arsenic III passes a reverse osmosis membrane far more readily and must be oxidised first.
The test that settles this is laboratory arsenic speciation analysis. We include what we can measure on site in a free water test, and we will tell you plainly when a certified laboratory is the right next step rather than anything we can do at your kitchen tap.
When not to treat it
If a speciated test comes back non-detect, retest on the normal annual cycle rather than installing equipment. Arsenic concentrations in a given well are usually stable, so a clean result is informative.
Treatment options that actually apply
These are the equipment types that address this problem. Each page states what the equipment does not do, so you can rule it out quickly if your situation does not match.
- Reverse osmosis, tank. A membrane system under the sink that produces treated water to a dedicated tap and stores it in a small pressure tank.
- Well water systems. A treatment train assembled around a current laboratory test, in stages.
What none of these will do
- Water at any tap other than the one it feeds. Showers and laundry are untouched.
- Hardness in the rest of the house, so scale continues elsewhere.
- Bacteria, unless the unit is specifically certified for it. Do not treat unsafe water with RO alone.
Getting it installed
Once a test has confirmed the problem and narrowed the equipment, the practical questions are access, space, and whether anyone's permission is needed. Those are covered on the installation pages, along with what a visit involves and how long it takes.
- Free water testing. 45 to 60 minutes.
- All installation services
- What installation costs
Other water problems
Sources
- Arsenic in Drinking Water. US Environmental Protection Agency, 2024.
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