A mitigation system pulls soil gas out from under the floor. It does nothing at all about the radon arriving through the taps — and in a county where most rural homes draw from fractured bedrock, that is not a hypothetical.
How radon gets into the water
The same uranium-bearing rock that produces soil gas beneath a house also holds the groundwater that supplies its well. Radon dissolves into that water underground and stays dissolved until the water is agitated at the surface — which is to say, until someone runs a shower, fills a bath, uses the dishwasher, or does the laundry. Then it comes out of solution into the air of the house.
Public water supplies generally lose most of their radon during treatment and storage before the water reaches anyone. Private wells, which is what most of rural Hunterdon County has, deliver the water straight from the rock to the tap.
How it usually surfaces here
Two ways. The first is a mitigation system that works, but not enough — the soil-gas system drops the reading substantially and it then stalls short of where it should be, particularly with readings that spike in and after the bathroom. The second is a sale. Under the Private Well Testing Act, a Hunterdon County home on a private well has to have its water tested when it changes hands, and gross alpha is a required parameter in this county. Gross alpha measures total alpha radioactivity from radium, uranium and radon together, so an elevated result is a prompt to test specifically for what is causing it.
That is the value of the requirement: for a lot of households, a routine transaction test is the first time anyone looks at the water side at all.
What treatment looks like
Aeration is the approach the EPA points to for high waterborne radon. Water is sprayed or bubbled in a vented tank at the point of entry, the radon comes out of solution and is vented outdoors, and a repressurisation pump puts the water back into the house at pressure. It typically runs in the region of $3,800 to $6,500 installed, needs annual servicing, and it belongs at the point of entry — treating one bathroom does nothing for the rest of the house.
Granular activated carbon is the cheaper option, roughly $1,200 to $2,200. Water passes through a carbon bed that adsorbs the radon. It is less effective at high concentrations, and the bed itself accumulates radioactivity over time, which affects where it can sensibly be sited and how it is eventually disposed of. A contractor should be straightforward with you about where the crossover between the two sits for your particular numbers rather than selling you whichever one they prefer to install.
Which houses should be asking
Any Hunterdon County home on a private well with an indoor reading that a soil-gas system did not fully explain. Any home whose gross alpha result came back elevated. And anywhere on the Highlands rock in the north of the county or the Lockatong argillite in the west, where the wells draw from precisely the formations that produce the radon in the first place.
Neither air nor water treatment substitutes for the other. They are two systems for two routes, and a complete answer sometimes means both.
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Get free quotes →General information for Hunterdon County, NJ property owners — not a diagnosis, not a quote, and not a reading for any particular building. Every property is different; a certified professional confirms specifics on site.