Most people figure arsenic in well water is a problem for somewhere else. The Ganges Delta, maybe, where deep tube wells went in decades ago and large numbers of people got poisoned by their own supply. That story is real. But the same element sits in the rock under plenty of American counties, and a well can test clean for bacteria and taste fine and still carry it. The belief that you would notice it is wrong.
The lab report is the only evidence
Arsenic is a chemical element, symbol As, atomic number 33. It is a metalloid in group 15, sharing properties with phosphorus and antimony. None of that matters at the kitchen tap except one thing: it seems to dissolve out of certain rock formations and stay dissolved.
The figure represents a concentration, not a feeling. You cannot sense one part per billion any more than you can sense a hundred. Some regions carry extraordinary loads. Most American wells are nowhere near that, but the only way to know where yours sits is a lab. Strips on the shelf by my back door cover chlorine, hardness and pH. They do not cover arsenic. Nothing cheap at the kitchen sink does.
Which form you have matters for removal. In neutral water, arsenic acid exists as the ions [HAsO4]2− and [H2AsO4]−, while arsenous acid is not ionized. A decent lab panel reports total arsenic, and the lab can tell you more if you ask. When I walk somebody through their numbers I start with reading a well water lab report, because the line that says arsenic, total, in micrograms per liter, is the whole ballgame. If you have never sent a sample, collecting a well water sample the right way is what keeps the result honest.
The sample decides everything
Here is the procedure. Call the county or state lab first and ask for their metals panel. They will tell you the bottle, the preservative if any, and the holding time. Then collect from a faucet as near to the well as possible, ahead of any softener or filter, since you need to learn what the well supplies, not what the pipes correct. Let the water flow for several minutes, fill the container, seal it, store it cold, and deliver it to the laboratory within their timeframe. Shipping a water sample to the lab is its own small job if the lab is not local, and holding times are not a suggestion.
If the number comes back under 10, write it in the household log with the date and retest on the lab’s schedule, not your hunch. Aquifers change. My wife has kept our log for years, and the value of it is the pattern, not any single page. If the number comes back over 10, do not treat it yourself. Call the well driller first, before any equipment. Treatment for arsenic is sized to the water, the flow rate and the form of the arsenic, and the wrong unit is money spent on water that is still over the limit. That is the trade-off every time, because treating blind costs more than testing twice.
On a service call in October 2022 I pulled the paperwork on a well the owner had drilled in 1998. Nobody had tested since. Nothing looked different, tasted different or behaved different at the tap. Total damage was the two lab panels, the system and a morning of my time, and they had been drinking it for about two decades in between. That detail lingers long after the rest fades. Not the number. The twenty years of not knowing.
Now that the problem is on the table, go watch the full video before you decide what your household needs. It walks through storage and treatment in order, the way I would do it at your place.
Should a neighbor ask me across the fence, I’d tell them: arsenic is the single pollutant I won’t estimate. It gives you nothing to sense, it is first on the federal hazard list for a reason, and the test is a bottle and a form and a trip to the lab. Test before you treat, treat only what the report says is there, and write the number down so the next test means something.
The steps I follow at my own place:
- Lab panel for metals including arsenic on the schedule the lab recommends, logged with the date.
- Sample drawn before any treatment, in the lab’s bottle, inside the lab’s holding time.
- If a number comes back high, a second sample to confirm before any equipment decision.
- Treatment sized by the driller to the confirmed number and the form of arsenic, then a follow-up test to prove the water.
- Stored water kept current regardless, because treatment is a machine and machines fail; my two drums in the garage get rotated twice a year whether the well is perfect or not.
Watch the full video now and follow it step by step at your own tap.