Radium in Well Water: The Public 5 pCi/L Line

By SubcontractorHub Editorial Team·Published October 2026

Dealers meet radium in well water when a radionuclide panel prints two activity lines, or when a gross alpha screen is the only number on the page. Those are different tests. The alpha screen, and why it is not uranium mass, is gross alpha in well water. Uranium's mass row is uranium in well water. This page is only combined radium. The national primary rules apply to public water systems.

Radium in Well Water on the Primary Table

The national primary drinking water regulations list Radium 226 and Radium 228 (combined). The MCLG cell reads “none” and “zero,” the same pattern as the alpha-particle row. The MCL is 5 pCi/L. The potential health effect listed is an increased risk of cancer. The source listed is erosion of natural deposits.

An MCL is the enforceable public standard. An MCLG is a non-enforceable health goal. The cell that prints both “none” and “zero” is not a second MCL under 5. Do not invent a goal of zero as a pass line for a private well. The 5 pCi/L figure is the number the table prints as the MCL.

Combined Means the Two Results Added

Section 141.66 of the 2025 Code of Federal Regulations states the maximum contaminant level for combined radium-226 and radium-228 is 5 pCi/L. It says the combined value is determined by the addition of the results of the analysis for radium-226 and the analysis for radium-228. If the lab printed only one isotope, you do not have the combined value yet. Do not treat the single line as if the other were zero unless the report says that.

Adding the two activities is not a unit conversion. Picocuries and becquerels are both activity, and that step is the picocurie becquerel converter. The tool does not decide a pass or a fail, and it does not turn activity into micrograms. Do not send a radium number through it and call the becquerel a uranium mass.

Four Rows People Put on One Line

The same section says the MCL for gross alpha particle activity, including radium-226 but excluding radon and uranium, is 15 pCi/L. Radium can be part of an alpha story and still needs its own combined result before you compare it with 5. A result of 5 is not a stricter version of 15. They answer different questions.

Uranium's MCL in that section is 30 µg/L. Beta particle and photon radioactivity is a dose limit of 4 millirem per year, with a calculation method this page does not run. Radon in water is a gas and a different test, on radon in well water. Do not file radium, radon, uranium, and gross alpha under one word, “radiation.”

What Is the Public Compliance Date for Combined Radium?

The regulation says community water systems must comply with the combined-radium MCL, the gross alpha MCL, the beta and photon MCL, and the uranium MCL beginning December 8, 2003. That sentence names community water systems. A private well is not that system. Some states borrow the federal number. This page does not invent a state rule it did not fetch.

Using 5 pCi/L as a label beside a household result is a benchmark. It does not become a violation, a pass, or a real-estate condition. Say that you are using the public line, and say whether both isotopes were on the sheet.

The Technology List Is Not a Percent

The same section identifies best available technologies for combined radium-226 and radium-228 as ion exchange, reverse osmosis, and lime softening. That is the regulation's list for achieving compliance with the public MCL. It does not state a removal percentage, a resin volume, or an installed price. Naming the list is not an instruction to sell one of those stages on a private well.

A softener sold as “the radium fix” because ion exchange appears in the list skips the lab. Hardness, iron, and the actual radium numbers still have to be on the ticket. This page does not size the bed. The gross-alpha guide's 0.67 divisor, which that other page refuses to run, is not used here either.

What to Write on the Ticket

1. Radium-226, radium-228, or both, with the unit the lab printed.
2. The sum, only if both results exist, set beside 5 pCi/L.
3. Gross alpha, if it was printed, left on its own 15 pCi/L comparison.
4. Uranium mass, if it was printed, left in micrograms per liter.
5. A note that 5 pCi/L is a public-system line, not a private-well statute.

Where Radium in Well Water Stops

This page does not convert picocuries of radium into a mass, and it does not predict a health outcome for a person who drinks the water. The cancer phrase is the table's phrase for long-term exposure above the MCL on a public system. It is not a diagnosis.

A water treatment dealer who writes both isotope results, or writes that one of them is missing, can price a later conversation without pretending the alpha screen was the radium test. Keep the activity unit on the line. Do not divide it by 1,000 and call the quotient micrograms.

Frequently Asked Questions