Getting an arsenic result is straightforward. Knowing what it obliges you to do next is where most well owners get stuck, because arsenic is not a contaminant where the answer is simply to fit a filter: the treatment depends on which chemical form is present, and a home kit does not tell you that.
A clear negative, and what it is worth
A home screen showing no color is genuinely reassuring, with one caveat: it is a snapshot. Arsenic concentration in a well moves with pumping rate, with the season and with any change to the water table, so a clean result establishes today rather than permanently. The EPA notes that private wells are not federally regulated under the Safe Drinking Water Act, so no one else is watching for the change. Retest annually, and retest sooner after any work on the well, any new well nearby, or a noticeable change in yield.
Any color at all means send it to a lab
Home kits are a screen, not a measurement. Sulfide interference, temperature and timing all shift the color, so a faint result may be an overstatement or an understatement, and neither is a basis for a decision. If a screen shows anything, commission a certified laboratory analysis, and ask specifically for speciation, meaning the split between arsenic three and arsenic five. Without that split a treatment system is being designed on a guess, and the wrong guess produces a system that removes very little of what is actually there.
Why the form decides the treatment
Arsenic five carries a charge that treatment media can grip, so it is removed well by reverse osmosis, by anion exchange and by adsorptive media such as iron oxide or activated alumina. Arsenic three is uncharged at typical groundwater pH and passes through most of those, so it must be oxidized to arsenic five first, usually with chlorine or a specific oxidizing filter, before anything can capture it. Well water is often reducing in character, which favors arsenic three, which is precisely why speciation matters on wells.
Choosing point of use or whole house
Arsenic is a concern from ingestion rather than from bathing, so a point of use system at the kitchen tap is a legitimate and much cheaper answer, provided every drinking and cooking outlet is covered and everyone in the household knows which tap is treated. Whole house treatment makes sense where that discipline is unrealistic, or where the treatment is being fitted anyway for other reasons. Whichever is chosen, test the treated water after commissioning and periodically after that. Our water test kit guide covers what else to test alongside.
Questions people ask about arsenic water test kit
My home kit showed no color, am I clear?
For today. Arsenic moves with pumping, season and water table, so retest annually and after any work on the well or change in yield.
It showed a faint color, what now?
Send a sample to a certified laboratory and ask for speciation. Home kits are a screen and cannot give a number you can design around.
Why does the form of arsenic matter so much?
Arsenic five is removed by reverse osmosis, anion exchange and adsorptive media. Arsenic three is uncharged and must be oxidized first.
Do I need whole house treatment?
Not necessarily. Arsenic is an ingestion concern, so point of use at the drinking and cooking taps is a legitimate and cheaper approach.