Hexavalent chromium, also called chromium-6, now has its own California drinking-water limit of 10 micrograms per liter. The City of San Diego 2025 report shows results below that limit at the plants and purchased water it lists. Read your serving utility’s current Consumer Confidence Report, then judge any filter by the exact model’s certified reduction claim.
What hexavalent chromium is
Hexavalent chromium is a form of the metal chromium that can enter water from industrial use and from natural processes.
The State Water Resources Control Board describes it as a heavy metal used in industry and found naturally in the environment. Citing OEHHA’s 2011 review, the Board states that the hexavalent form has been shown to be carcinogenic and toxic to the liver. California lists it under Proposition 65 as a chemical known to the state to cause cancer.
That’s public-health language from those agencies, not a diagnosis of your tap. For personal health questions, use those sources or a licensed clinician. People often search this name after the Erin Brockovich case. That history isn’t a San Diego tap measurement.
The City’s 2025 report notes hexavalent chromium can form when naturally occurring trivalent chromium is transformed by natural and human processes. That’s a source note, not a countywide count.
The California limit versus the federal total-chromium rule
California now sets a hexavalent-chromium-only maximum contaminant level, or MCL. The federal government still regulates total chromium, not chromium-6 by itself.
The Water Board’s hexavalent chromium MCL is 0.010 milligrams per liter, or 10 micrograms per liter. The public health goal, or PHG, is 0.02 micrograms per liter, set in 2011. The rulemaking took effect October 1, 2024. There’s no federal hexavalent-only MCL.
An MCL is the enforceable limit for public systems. A PHG is a health-based goal used in California rulemaking. Don’t treat the PHG as the legal limit.
California’s total chromium MCL remains 50 micrograms per liter. The federal total chromium MCL is 100 micrograms per liter. The Water Board says California kept the lower total-chromium number after EPA raised the federal MCL in 1991. Older “no chromium-6 MCL” pages are out of date.
What the City of San Diego 2025 report shows
The City of San Diego 2025 report lists hexavalent chromium below the 10 ppb MCL for the plants and purchased water it reports.
The 2025 Annual Drinking Water Quality Report covers Public Water System 3710020. Hexavalent chromium is listed in ppb. The printed MCL is 10 ppb, matching California’s 10 micrograms per liter. The PHG is 0.02, and the detection limit is 0.1 ppb. See also the City water-quality portal.
| Source in the 2025 City report | Hexavalent chromium (ppb) |
|---|---|
| Alvarado plant | Not detected |
| Miramar plant | Not detected |
| Otay plant | Not detected |
| Purchased treated water | Average 0.1, range not detected to 0.4 |
| California MCL | 10 |
| PHG | 0.02 |
Purchased-water results sit below the 10 ppb MCL. “Not detected” means the laboratory didn’t find it at or above the 0.1 ppb reporting limit. This table isn’t a countywide figure, a private-well result, or a tap test for every City address. A CCR describes the public system and period named in the document.
Plumbing inside a building can still change what reaches a fixture. That’s why lead in San Diego drinking water and San Diego tap water safety are separate questions.
How to check a different water district or a well
If the City of San Diego doesn’t serve the address, use that other utility’s current Consumer Confidence Report.
San Diego County has many public water systems. A City plant result doesn’t describe another district or a private well. Find the utility name on a recent bill, then open that utility’s latest report and notices.
The Water Board points readers to annual reports and to Drinking Water Watch. Match the system name, report year, hexavalent versus total chromium, units, printed MCL, range, and any violation. Don’t mix the two chromium rows. Don’t compare numbers until the units match.
A private well isn’t covered by a city or district report. CDC well-testing guidance says to use a state-certified laboratory and to ask local health officials which extra tests fit the location. CDC’s routine annual list is total coliform, nitrate, total dissolved solids, and pH. Hexavalent chromium isn’t on that short list. If chromium-6 is the concern, ask which method reports hexavalent chromium, not only total chromium. A field meter isn’t a hexavalent chromium laboratory result.
Treatment claims to verify on the exact model
Don’t assume every reverse osmosis unit, whole-house filter, or pitcher reduces chromium-6.
EPA’s home-treatment guide states that no single technology removes every contaminant. NSF/ANSI 53 covers specified health-effect contaminant claims. NSF/ANSI 58 covers reverse osmosis systems. Certification to a standard isn’t a ranking, and it doesn’t mean every listed model reduces hexavalent chromium. You still need the exact model’s current listing and performance data sheet.
Use the same method as checking a filter’s certified claim. Write down the full model number. Open the certifier’s listing. Match the contaminant language to that model and replacement element.
Pitcher carbon filters aren’t automatically sufficient. Many are certified only for taste and odor. If a pitcher or a reverse osmosis drinking water system is offered for chromium-6, require that model’s hexavalent chromium reduction claim in writing.
Don’t accept an invented removal percentage. Point-of-use devices treat a selected tap. Point-of-entry systems treat water entering the residence. A water softener reduces hardness ions. Don’t treat it as chromium-6 treatment without an exact certified claim.
Request a local referral
Filter Pros San Diego refers homeowners to separately licensed water-treatment professionals for a local visit. You contract with and pay the provider directly. This site doesn’t install equipment, interpret medical risk, or certify that a referred system reduces chromium-6.
Bring the current utility report, or a well laboratory report if you have one. Ask for the exact model number, certified reduction claim, performance data sheet, replacement parts, and a written scope. A free in-home water test can document basic field conditions. Confirm what that visit measures. It isn’t a hexavalent chromium laboratory analysis, and it doesn’t declare tap water safe.
Call (858) 400-6508 to request a local referral.
Frequently asked questions
The short answers below repeat the 2024 California limit, the City 2025 table, and the exact-model rule.
Does San Diego tap water have chromium-6?
The City 2025 report lists Alvarado, Miramar, and Otay as not detected and purchased treated water at 0.1 ppb average, range not detected to 0.4, below the 10 ppb MCL. That isn’t countywide. Other districts and wells need their own reports or lab samples.
Is there a federal chromium-6 drinking-water limit?
There’s no federal hexavalent-only MCL. EPA’s total chromium MCL is 100 micrograms per liter. California’s hexavalent chromium MCL is 10 micrograms per liter, effective October 1, 2024. California’s total chromium MCL remains 50 micrograms per liter.
Do pitcher filters remove chromium-6?
Not automatically. Many pitchers are certified for taste and odor only. Require the exact model’s current certified hexavalent chromium reduction claim and performance data sheet.
Does reverse osmosis remove chromium-6?
Only if the exact RO model lists a certified reduction claim for it. NSF/ANSI 58 covers reverse osmosis systems as a category. That category label isn’t a chromium-6 claim for every unit.
Should I test a private well for chromium-6?
A city or district report doesn’t describe a well. Use a state-certified laboratory. Ask which method reports hexavalent chromium, and follow local health-department guidance on whether that test fits the property.