Water Quality Data
Radium in San Fernando Valley Tap Water: What LADWP and Las Virgenes MWD Report
Radium is a naturally occurring radioactive element that enters drinking water primarily through groundwater contact with rock and soil formations. The EPA set a combined Maximum Contaminant Level of 5 picocuries per liter for radium-226 and radium-228 under the Radionuclides Rule, finalized in 2000 and effective December 2003 (EPA Radionuclides Rule). Both LADWP and Las Virgenes Municipal Water District monitor for radium and disclose detections in their annual Consumer Confidence Reports. The San Fernando Valley receives a blended supply that includes Colorado River water, State Water Project water, and local groundwater from the SFV groundwater basin. Because surface water typically carries lower radium concentrations than groundwater, the proportion of each source in the blend affects what customers receive at any given address. The dataset below summarizes the federal regulatory limits. For address-level numbers, the utility CCR is the primary document.
EPA Radionuclides Rule: MCLs for Radium and Related Parameters
Compiled from 40 CFR 141.66. All limits apply to community water systems serving 25 or more persons. Effective December 2003.
| Parameter | EPA MCL | Unit | Notes |
|---|---|---|---|
| Combined Ra-226 + Ra-228 | 5 | pCi/L | Sum of both isotopes must not exceed 5 pCi/L |
| Gross alpha particle activity | 15 | pCi/L | Excludes radon and uranium; includes Ra-226 |
| Gross beta and photon radioactivity | 4 | mrem/yr | Annual dose equivalent at the tap |
| Uranium | 30 | µg/L | Regulated for chemical, not radiological, toxicity |
Sources: EPA Radionuclides Drinking Water Rule; 40 CFR 141.66 (eCFR). pCi/L = picocuries per liter. mrem/yr = millirems per year. µg/L = micrograms per liter.
What radium is and how it enters the SFV water supply
Radium-226 and radium-228 are naturally occurring radioactive isotopes in the uranium and thorium decay chains respectively. They are present in varying concentrations in soil and rock throughout California, and they dissolve into groundwater as water moves through those formations. Surface water sources, including the Colorado River and the State Water Project aqueduct that brings water from Northern California, generally have lower radium concentrations because they spend less contact time in direct contact with mineral-rich substrates.
The SFV groundwater basin underlies much of Woodland Hills, Canoga Park, West Hills, Reseda, and Chatsworth. When LADWP draws from local SFV wells, that water typically carries different radionuclide characteristics than imported surface water. LADWP blends sources depending on seasonal availability, state water allocations, and reservoir levels, which means the radium contribution to any given distribution zone shifts over time. Customers in areas served primarily by SFV groundwater may see different monitoring results than those served primarily by imported surface water, even within the same utility.
How LADWP and Las Virgenes MWD monitor for radium
Under the Safe Drinking Water Act and the EPA Radionuclides Rule, community water systems are required to monitor for radionuclides at a frequency determined by their population size, source type, and previous monitoring results. Large systems like LADWP monitor more frequently than smaller systems. Systems with no prior detections above 50 percent of the MCL may qualify for reduced monitoring schedules; systems with detections near or above the MCL must increase monitoring frequency.
Both LADWP and Las Virgenes Municipal Water District are required to include radionuclide detection data in their annual Consumer Confidence Reports. The CCR lists the contaminant, the detection level found, the EPA MCL, and whether the utility is in compliance. LADWP's CCR is published at ladwp.com/water-quality and LVMWD's at lvmwd.com/water-quality. Both documents are updated annually. Our separate article on SFV water quality by source explains how to navigate a Consumer Confidence Report and where the radionuclide table appears.
How radium-226 and radium-228 differ, and why both are measured
Radium-226 is an alpha emitter. Its primary health concern is internal exposure through ingestion: when ingested, radium behaves biochemically like calcium and can deposit in bone tissue, where it irradiates surrounding cells. The EPA gross alpha MCL of 15 pCi/L serves partly as a screen for radium-226, since radium-226 contributes to gross alpha activity and triggering gross alpha monitoring prompts more specific analysis.
Radium-228 is a beta emitter and a decay product of thorium-232. Because beta radioactivity is not captured in gross alpha screening, radium-228 requires its own separate analysis. The combined MCL of 5 pCi/L for both isotopes means utilities must add the radium-226 result and the radium-228 result and compare the sum to 5 pCi/L. A utility with 3 pCi/L of radium-226 and 3 pCi/L of radium-228 would be in violation of the MCL even though neither individual reading exceeds it.
What treatment removes radium from drinking water?
The EPA has evaluated several treatment technologies for radium removal, based on data compiled in its Drinking Water Treatment Technology guidance. The most effective technologies for community-scale and point-of-use radium reduction include:
- Ion exchange (strong acid cation resin): The same resin used in conventional water softeners removes radium by exchanging it for sodium or potassium ions. This is one of the primary treatment methods used by utilities to address elevated radium. At the point of entry to a home, a properly sized ion exchange system can reduce radium-226 and radium-228 significantly.
- Reverse osmosis: Systems certified under NSF/ANSI 58 with a radium reduction claim are effective at the point of use for drinking and cooking water. Noohi installs reverse osmosis systems throughout the SFV; a kitchen-tap RO is the most common point-of-use solution for households concerned about radionuclides in drinking water.
- Lime softening: Used at the utility scale. Raising pH with lime causes radium to co-precipitate with calcium carbonate. Not a point-of-use technology.
Standard carbon block filters, sediment filters, and pitcher filters are not rated for radium reduction. If radium is the primary concern, verify that a system's NSF certification specifically lists radium-226, radium-228, or combined radium in its contaminant reduction certificate, not just TDS or general minerals.
Should SFV homeowners test their tap water for radium?
For most SFV homeowners served by LADWP or LVMWD, the utility's CCR provides the distribution-system answer. If the reported combined radium level is well below 5 pCi/L and the utility is in compliance, the tap water meets the federal standard. The CCR is free, updated annually, and covers the distribution system as a whole.
Point-of-use testing at a specific address makes more sense in three situations: the home has a private well, the home is on a small water system not subject to the same monitoring frequency as large utilities, or the homeowner wants to verify that conditions at the tap match distribution-system averages. Radium testing requires a laboratory analysis; it is not a field-kit parameter. California maintains a searchable directory of state-certified laboratories at waterboards.ca.gov/drinking_water/certlic/labs/. For utility customers, the CCR is the right starting point before investing in lab testing.
Our related articles cover the other radiological parameters tested in SFV water: uranium and gross alpha in SFV tap water and the 2026 SFV water quality overview. A free in-home consultation covers the standard tap parameters at your address and can help determine whether additional lab testing makes sense for your household.
Sources used in this article: EPA Radionuclides Drinking Water Rule; 40 CFR 141.66: Maximum Contaminant Levels for Radionuclides (eCFR); EPA Drinking Water Treatment Technology guidance; NSF International: Certified Water Filters; LADWP Consumer Confidence Reports; Las Virgenes MWD Consumer Confidence Reports; California SWRCB: Certified Drinking Water Laboratories.
Frequently Asked Questions About Radium and SFV Drinking Water
What is the EPA limit for radium in drinking water?
The EPA Maximum Contaminant Level for combined radium-226 and radium-228 is 5 picocuries per liter (pCi/L), set under the Radionuclides Rule effective December 2003. There is a separate gross alpha particle activity MCL of 15 pCi/L, which includes radium-226 but excludes radon and uranium.
Does LADWP test for radium?
Yes. LADWP is required to monitor for radium-226, radium-228, and gross alpha particle activity under the Safe Drinking Water Act and the EPA Radionuclides Rule. Detection results and their comparison to the MCL are disclosed in the annual Consumer Confidence Report published at ladwp.com/water-quality.
Is radium in tap water dangerous?
Radium is a radioactive element classified by the EPA as a carcinogen, primarily associated with increased bone cancer risk from long-term ingestion above the MCL. Water delivered below the 5 pCi/L MCL meets the enforceable federal standard. For address-specific data, consult the utility's Consumer Confidence Report and, if needed, a certified laboratory analysis.
Does groundwater have more radium than surface water?
Generally yes. Radium occurs naturally in rock formations and leaches into groundwater through prolonged contact. Surface water sources such as the Colorado River and State Water Project water typically carry lower radium concentrations. The SFV receives a blended supply, so the proportion of local groundwater in the blend affects average radium levels.
What home treatment removes radium from drinking water?
Reverse osmosis systems certified under NSF/ANSI 58 with radium reduction claims are among the most reliable point-of-use options. Ion exchange using a strong acid cation resin, the same technology used in conventional water softeners, is also effective for radium-226 and radium-228. Standard carbon block filters and sediment filters are not rated for radium reduction.
