Radon in well water in Licking and Union counties: what to test

Your house sits on a few acres outside Granville, Johnstown, Pataskala, Galena, Sunbury, Marysville or Plain City, the water comes from your own well, and someone has asked whether that well has radon. It is a fair question, and it has a sensible order of operations: settle the air first, then decide about the water. The same path works anywhere in rural Madison and Union counties.

Step 1: test the air before the water

A house on a well can take in radon two ways: as soil gas seeping through the foundation, and as gas dissolved in groundwater that escapes when the water runs. EPA's guidance is that soil gas is usually the much larger risk of the two. Most of the risk from waterborne radon comes from breathing what escapes into the air during showers, dishwashing and laundry, rather than from drinking it. Homes on surface-water supplies, such as a utility drawing from a river or reservoir, usually have no water radon problem at all.

The ground out here gives soil gas plenty to work with. EPA maps Licking, Union, Madison and Delaware counties in Zone 1, its top radon category. In the 1988-89 state screening survey, 72 percent of the 29 Licking County homes tested read above 4 pCi/L. Union and Madison had only 6 and 10 homes tested, far too few to read anything comforting into.

So the first move is an ordinary indoor air test on the lowest floor that is lived on, or could be, in a room people actually use. Ohio's measurement protocol keeps the detector out of bathrooms, kitchens and laundry rooms, the same rooms where water use happens. The free state kit offered through ohio.radon.com, a charcoal canister from the hardware store, or a professional test through our radon testing service all get you that number.

Step 2: decide whether the water needs its own test

Here is the gap most well owners never hear about. Ohio's private water system rules, OAC 3701-28, cover well construction, permits and sampling through local boards of health, but they set no radon limit for private wells. Nothing in that routine requires a radon result, so a well rarely gets one unless the owner asks. Around here the local boards include the Licking County Health Department, the Union County Health Department and the Delaware Public Health District.

Reasons to go ahead and sample the water:

• Your air result came back at 4 pCi/L or higher, and you want to know whether the well belongs in the picture before choosing a fix.
• A soil-gas system is running with a steady gauge, and the air still reads higher than you expected.
• You are buying rural property and want the whole picture before closing.
• You simply want to know, which is reason enough.

How the sample is drawn matters as much as which lab reads it, because radon escapes from water readily once it is splashed or stirred. ANSI/AARST publishes a standard for measuring radon in water, MW-RN-2020, and Ohio licenses both radon testers and radon labs. Ask whoever samples your well which method they follow and which Ohio-licensed lab will run it.

Step 3: read the water result next to the air result

A water number by itself does not make the decision. Pair it with the air test:

• Air high, water low: the fix is ordinary soil-gas mitigation under the slab or in the crawlspace, and the well is not the problem.
• Air high, water elevated: deal with the soil gas first, since it is usually the bigger risk, then weigh water treatment.
• Air under 4, water elevated: treatment can still be worth weighing, because that radon reaches your lungs through the shower and the laundry.
• Both low: keep retesting the air every two years, which is ODH's schedule for single-family homes, and after any major renovation.

With no Ohio radon limit for private wells, the water decision is yours to make, so make it with both numbers in front of you. Our FAQ on radon in well water takes the common follow-up questions one at a time.

Step 4: point-of-entry or point-of-use treatment

EPA notes that private wells can be treated at the point of entry, where water comes into the house, before it reaches any tap. A point-of-use unit serves a single faucet, which fits radon poorly: the risk comes mostly from gas released in the shower and the laundry, and a filter under the kitchen sink never touches those.

For radon, treating the whole house supply at the point of entry is the approach that matches where the risk actually is. The two methods EPA describes:

• Aeration, which agitates the water to drive radon out and vents the released gas outdoors. EPA puts typical reduction at 95 to 99 percent.
• Granular activated carbon (GAC), a tank that captures radon as water passes through it, with typical reduction of 85 to 95 percent. EPA describes it as suited to moderate levels, around 5,000 pCi/L or less in the water, and warns that radioactive by-products build up on the carbon, which affects where the tank sits and how spent carbon gets handled.

Which one fits depends on the level in your water and how the system can be installed, which is why the water result from step 2 comes before any equipment decision.

What the local geology does and does not say

The highest groundwater radon in the USGS Ohio chapter was found far from here: up to 3,000 pCi/L in water tied to the Huron Member of the Ohio Shale in Erie, Huron and Seneca counties, up in northern Ohio. That finding describes northern Ohio, not Licking or Union County.

That is a reason for calm, not a reason to skip the test. Groundwater radon can differ from one well to the next, and the air in a Granville farmhouse or a Plain City ranch is still Zone 1 air. The order stays the same everywhere: the air tells you most of what you need, and the water test answers the rest.

Your next step: start with the air. Order the free state kit or book a professional short-term test ($150 to $300). If you live in Granville, Plain City or anywhere on a well in between, call or text us with your air result and we will help you line up whatever comes next.