TL;DR

Why chromium shows up in wells

Chromium occurs naturally in rock and soil and is also associated with industrial uses such as plating, stainless steel production, and pigments. Groundwater can acquire dissolved chromium through natural weathering or from legacy industrial releases. The oxidation state matters: Cr(III) is less mobile and an essential nutrient in trace amounts; Cr(VI) is more mobile and toxic. Aquifer chemistry (pH, redox) can shift chromium between these states, so speciation—the form it’s in—matters for risk and treatment.

Health context (in plain English)

Hexavalent chromium (Cr(VI)) compounds are classified as carcinogenic to humans by leading health agencies. While much of the evidence comes from inhalation in workplaces, drinking‑water risk management still aims to keep Cr(VI) as low as feasible. If your well has chromium, focus on measuring Cr(VI) and choosing a treatment that specifically reduces it.

Standards & what “safe” means right now

• U.S. federal standard (public systems): The EPA’s enforceable MCL for total chromium (Cr(III)+Cr(VI)) is 0.1 mg/L (100 ppb). This applies to public water systems; private wells are not covered.
• California (public systems): California adopted a specific MCL for hexavalent chromium at 10 µg/L (10 ppb) effective October 1, 2024. Private wells aren’t required to meet it, but many homeowners use 10 ppb as a protective target.
• Public Health Goal (context): California’s PHG for Cr(VI) is 0.02 µg/L. That level is risk‑based and generally not achievable in typical home treatment scenarios—it’s a context point, not a practical expectation.

Benchmarking tip: If Cr(VI) is at or above 10 µg/L, consider treatment. Even below that, many homeowners choose RO at the kitchen tap to minimize exposure during drinking and cooking.

Testing: what to order, how to sample, how to read results

1) Order the right tests

• Total chromium (commonly by ICP‑MS; e.g., EPA 200.8)
• Hexavalent chromium (Cr(VI)) (commonly by ion chromatography; e.g., EPA 218.6/218.7)

2) Sample, preserve, ship correctly

Cr(VI) can shift to Cr(III) if a sample isn’t handled correctly. For Cr(VI) methods, labs typically require immediate filtration (0.45 µm) and buffering to pH 9–9.5. Use the lab’s bottles and follow instructions precisely—this prevents false‑low results.

3) How often should I test?

As a baseline, test private wells annually for core indicators and any contaminants of local concern. Add chromium when geology or land use suggests risk or when previous results found chromium. Re‑test after installing treatment (and periodically) to confirm performance.

4) Interpreting results

• Total chromium < 100 ppb and very low/undetected Cr(VI): within the federal public‑system benchmark (informational for private wells).
• Cr(VI) ≥ 10 ppb: above California’s public‑system MCL; many homeowners treat to meet or beat this level.
• Any detectable chromium: POU RO at the drinking tap is a prudent step; see treatment options below.

Treatment that really works for chromium

Reverse osmosis (RO) — Point‑of‑Use

RO is a widely recommended solution for reducing dissolved ions, including Cr(VI), at a drinking/cooking tap. Look for systems evaluated to NSF/ANSI 58 for performance claims. Pair with sediment and carbon prefilters and maintain per schedule.

Anion exchange — Point‑of‑Entry or Point‑of‑Use

Anion exchange resins can remove Cr(VI) (chromate/dichromate). Effectiveness depends on water chemistry and competing anions like sulfate or nitrate. For whole‑home coverage, anion exchange is often practical; many homeowners still keep an RO tap for polishing and taste.

Distillation

Effective but slow and energy‑intensive. Often considered a backup rather than a primary household solution.

Avoid common pitfalls (including a note on water softeners)

• Don’t rely on a water softener for chromium. Softeners are cation‑exchange devices for hardness (calcium, magnesium). They do not remove anions like chromate.
• Boiling doesn’t remove dissolved metals. It concentrates them as water evaporates.
• Activated carbon alone isn’t enough for Cr(VI). Use RO or anion exchange as your primary chromium treatment.
• Speciation matters. If you only have total chromium data, consider testing for Cr(VI) before choosing an anion‑exchange strategy.

Product picks you can actually buy (links verified)

Links below point to WaterSoftenerPlus.com and were verified accessible on October 20, 2025. Always match capacity and configuration to your home and confirm any certification paperwork before purchasing.

Reminder: NSF/ANSI/CAN 61 is a material‑safety standard; it does not prove contaminant reduction. For RO reduction claims, look for NSF/ANSI 58 or request the specific data sheet.

A step‑by‑step action plan for well owners

1. Check your risk profile. Consider nearby industry, geology, or neighbor results.
2. Order lab tests: total chromium and hexavalent chromium (Cr(VI)); ask for preserved bottles and written instructions.
3. Interpret results pragmatically. Use 100 ppb (total chromium) as the federal benchmark for public systems and 10 ppb (Cr(VI)) as a protective target for households.
4. Pick a treatment strategy. POU RO for drinking/cooking; anion exchange for whole‑home when warranted. Keep RO at the kitchen tap even with POE treatment.
5. Install and verify. Re‑test at the treated tap(s) to document performance.
6. Schedule maintenance. Put filter changes and follow‑up testing on your calendar.

Maintenance & monitoring

• Prefilters (sediment/carbon): 6–12 months depending on usage and turbidity.
• RO membrane: usually 2–5 years, influenced by feed‑water TDS, hardness, and pretreatment quality.
• Anion exchange resin: run length depends on competing anions (sulfate, nitrate, bicarbonate). Use follow‑up Cr(VI) testing to set service intervals.
• Post‑install testing: re‑check Cr(VI) after 2–3 months to confirm stability, then annually or at the first sign of taste/flow change.

Frequently asked questions

Is Cr(VI) the same as “chromium‑6”?

Yes. Both terms refer to hexavalent chromium in the +6 oxidation state.

My total chromium is low—do I still need Cr(VI) testing?

If total chromium is near detection and there’s no local source, speciation may be optional. If you’re in a risk area or plan anion exchange, order the Cr(VI) test.

Will boiling remove chromium?

No. Boiling concentrates dissolved metals as water evaporates.

Can a water softener remove chromium?

No. Softeners remove hardness cations; they don’t target anions like chromate. Use RO or anion exchange instead.

What certifications should I look for?

For RO, look for NSF/ANSI 58 (performance). For materials that contact drinking water, NSF/ANSI/CAN 61 addresses material safety, not reduction performance.

Is there a tougher benchmark than 10 µg/L?

California’s Public Health Goal for Cr(VI) is 0.02 µg/L. It’s informative but not typically achievable in routine home treatment.

Verified product links (WaterSoftenerPlus.com)

• Nelsen Reverse Osmosis System — 5 Stage, 50 GPD
• Under‑Sink Alkaline RO Water Filter (50 GPD class)
• Under‑Sink Reverse Osmosis (RO) Collection
• FluorideRemovalPlus (specialty media)
• ArsenicSafePlus (specialty media)

If any link format changes, replace it here and in the product cards above.