Radium in Well Water: What Your Result Means
If your well report lists gross alpha, radium-226 or radium-228, the numbers can mislead you in both directions. A low gross alpha result can still hide radium-228, and a high one may be mostly uranium rather than radium. Here's how the lines fit together, which follow-up test closes the gap, and what actually takes radium out of the water.
Radium itself is a naturally occurring radioactive metal that forms as uranium and thorium in rock break down. The U.S. Environmental Protection Agency notes that where rocks and soils hold more radium, the groundwater typically carries more of it too, and that chronic exposure to high levels can increase the incidence of bone, liver or breast cancer. You can't see, smell or taste it. EPA also notes that radium in water from community water systems is regulated while private wells aren't, so reading the report falls to you.
Acidic water is one warning sign worth knowing. The U.S. Geological Survey explains that low pH lets more radium stay dissolved in groundwater, and in one southeastern Pennsylvania rock formation it studied, every well sample with a pH below 4.7 was over the 5 pCi/L limit.
How the Radioactivity Lines on Your Report Fit Together
A radiological panel can list four or five separate lines. They overlap, but they aren't interchangeable. There's no federal limit for a private well, because EPA explains that private well water isn't regulated under the Safe Drinking Water Act. The limits public water systems have to meet are still the most useful yardstick, and they're set out in 40 CFR 141.66.
| Line on your report | What it measures | Public water benchmark |
|---|---|---|
| Gross alpha (pCi/L) | All alpha radiation in the sample at once, from radium-226, uranium and other alpha emitters | 15 pCi/L, a standard that counts radium-226 but sets radon and uranium aside |
| Radium-226 (pCi/L) | Radium from the uranium decay series | Added to radium-228 for the combined limit |
| Radium-228 (pCi/L) | Radium from the thorium decay series, a beta emitter that a gross alpha count doesn't see | Added to radium-226 for the combined limit |
| Combined radium (pCi/L) | Radium-226 plus radium-228 | 5 pCi/L |
| Uranium (µg/L) | Uranium measured by weight | 30 µg/L |
Some panels add a gross beta line. The federal beta standard is written as a yearly dose of 4 millirem from man-made beta emitters, not as a pCi/L number, so a gross beta count can't be read straight against it. Radium-228 is a natural beta emitter, and it's covered by the combined radium limit instead.
A low gross alpha result doesn't clear radium-228
Gross alpha is a cheap, useful screen, and it tracks radium-226 well. It can't see radium-228 at all. The U.S. Geological Survey describes gross alpha as a good screening tool for radium-226 and radium-224 "but not radium-228, which is a beta emitter." A reassuring gross alpha number answers half of the radium question, not all of it.
A high gross alpha result isn't automatically radium
The opposite mistake is just as easy to make. The lab's gross alpha measurement counts alpha activity from everything in the sample, uranium included. Only the 15 pCi/L standard sets uranium and radon aside. So a high gross alpha result could be mostly radium-226, mostly uranium, or a mix of both, and the number alone won't tell you which. Our guide to uranium in well water covers the uranium side, including why a gross alpha number can't be converted into a uranium level.
From Your Result to the Next Test
Public water systems work from a shortcut written into federal monitoring rules. Under 40 CFR 141.26, a gross alpha measurement "may be substituted for the required radium-226 measurement provided that the measured gross alpha particle activity does not exceed 5 pCi/l." The same rule requires that measurement to carry a 95 percent confidence interval, and there's no matching shortcut for radium-228. Borrowing that logic gives a well owner a workable path:
- Gross alpha at or below 5 pCi/L. Good news for radium-226, as long as the margin of error the lab prints beside it doesn't carry it past 5 (a result of 4 ± 2 does). It says nothing about radium-228. If your well has never had a radium-228 test, one is worth doing once, and sooner if wells near you have turned up radium or your county or state health department flags it in your area.
- Gross alpha above 5 pCi/L. Ask the lab for radium-226 and radium-228 as two separate results, then add them together for your combined number. Add a uranium test too, since uranium may be part of what the gross alpha line picked up.
- Gross alpha above 15 pCi/L. The same follow-up tests, sooner rather than later. Don't choose treatment until you know how much of the activity is radium and how much is uranium.
- Combined radium above 5 pCi/L. Your well is over the benchmark public water has to meet. Treat at least the water you drink and cook with, and read the next section before choosing how.
Crystal Quest®'s Radiological Water Test reports both radium isotopes only in its Deluxe tier ($565). The Basic ($179) and Standard ($219) tiers cover uranium, gross alpha and gross beta, and Standard adds radon-222. The sample goes back by next-day shipping. Whichever lab you use, ask for radium-226 and radium-228 as separate results so you can add them yourself.
What Removes Radium From Well Water
Federal rules list ion exchange, reverse osmosis and lime softening as the best available technologies for combined radium at public water systems. For gross alpha, they list only one: reverse osmosis (40 CFR 141.66). At home, EPA's guidance on natural radionuclides in private wells narrows it to two. Of the point-of-use systems available, the two EPA has found to work well are ion exchange and reverse osmosis.
Reverse osmosis at the kitchen tap
For radium, and especially for a high gross alpha result, reverse osmosis is the treatment we recommend first. It's the one technology the federal rules list for both combined radium and gross alpha, and the same table lists it for uranium too. An under-sink system treats the water at the tap you drink and cook from. Our explainer on what reverse osmosis removes covers how the membrane does it.
Whatever system you choose, ask for performance data that names radium and was measured on the model you're buying, then confirm it with your own retest of the treated water.
Ion exchange: a water softener or dedicated radium media
A conventional water softener can help. The USGS notes that "radium can be removed from a household water supply with an ion exchange water softener." If you already own one, test the softened water before you buy anything else, because it may already be lowering your radium.
If you'd rather treat every tap, or uranium came back high along with radium, look at the Radium & Uranium Whole House Water Filter (from $2,389). Water passes a sediment cartridge first, then a tank of specialized ion exchange media that cleans itself on an automatic backwash schedule, then a carbon cartridge. Versions with a softener or a SMART filter added are available. It isn't built for radon.
Plan for what the filter catches
Radium doesn't vanish when it's filtered out. It collects in the cartridge, membrane or media. EPA's private well guidance says of point-of-use systems: "Often, they collect too much radiation to be disposed of with ordinary trash." The company that installs the system, or your state radiation and solid waste offices, can tell you how to dispose of spent parts. Ask before you install, not after.
Test for radon, too
Radium breaks down into radon, a radioactive gas, and EPA notes that uranium, radium and radon can all dissolve into well water. Radon is a separate decision with its own test and its own treatment, and neither system above is built for it. Our guide to radon in well water walks through that one.
Retest After Treatment, Then Keep Testing
Once a system is in, test the treated water for radium-226 and radium-228, taken from the tap the system feeds. That's the result that tells you whether it's working on your water. After that, EPA advises private well owners to test for radionuclides every three years. Keep a raw well sample in that rotation too, so you'll notice if the well itself changes.
Radium is only one line on a well report. Our guide to testing well water covers the rest of what a private well should be checked for.
Get both radium numbers before you buy.
A radiological panel with radium-226 and radium-228 shows whether you're dealing with radium, uranium or both, so treatment fits the water you actually have.
