Arsenic in well water: limits, testing and treatment
Short answer
Arsenic has no taste, smell or color, so only a lab test finds it. EPA's limit for public water is 10 parts per billion (0.010 mg/L). If your well is above it, the usual fix is a reverse osmosis system at the kitchen tap certified to NSF/ANSI 58 for arsenic. Whole-house treatment uses adsorption media and is usually designed by a local pro.
Above 10 ppb: use bottled water for drinking and cooking until treatment is installed and a retest confirms it works.
Why arsenic is common in wells
Arsenic dissolves from natural rock formations. A USGS study of about 2,100 private wells found that roughly 23% had at least one contaminant at a level of potential health concern, and arsenic was among the most common, along with radon, uranium and manganese.
Treatment options
| Option | Covers | Notes |
|---|---|---|
| Reverse osmosis at the kitchen tap | Drinking and cooking water | Choose one certified to NSF/ANSI 58 for arsenic. Most effective on arsenic V; arsenic III may need oxidation first |
| Whole-house adsorption media | Every tap | Iron-based media; sized by a pro from your full test |
| Oxidation + filtration | Every tap, when iron is also present | Iron filters can remove some arsenic along with iron; confirm with a retest |
Ask your lab whether it can split arsenic into arsenic III and arsenic V. It changes which treatment works best.
Retest after treatment
Test the treated water after installation and then yearly. Arsenic treatment fails quietly when media is spent.
Questions well owners ask
Can you shower in well water with arsenic?
Arsenic is mainly a concern when swallowed; skin absorption is low. Drinking and cooking water are the priority, which is why a point-of-use RO system is the common fix.
Does boiling remove arsenic?
No. Boiling concentrates it as water evaporates.