Chromium-6 in Kent County Homes: Understanding Public Water Data for Dover, DE

The Dover Water Department in Kent County, Delaware, serves nearly 40,000 people with groundwater-sourced public water. Between 2014 and 2015, federal monitoring detected chromium-6 (also called hexavalent chromium or Cr(VI)) in a fraction of system samples. Five of 36 tests found chromium-6 above the reporting level of 0.03 micrograms per liter (ppb), with the highest at 1.7 micrograms per liter and a median detection value of 0.39 micrograms per liter. These detections are measurements, not regulatory violations, as no federal maximum contaminant level applies specifically to chromium-6. Total chromium was also measured separately with four detections above 0.2 micrograms per liter and the highest total chromium at 1.8 micrograms per liter—well below the total chromium MCL of 100 micrograms per liter.

If you know total chromium but not chromium-6, what does that mean?

Total chromium measurements combine trivalent chromium (chromium III) and hexavalent chromium (chromium VI) but do not specify their individual concentrations. The two forms differ chemically and in health considerations. Trivalent chromium is naturally occurring and generally not a health concern, while chromium-6 can be more chemically active. Therefore, a total chromium test alone cannot determine the presence or concentration of chromium-6 in your home’s water. To understand chromium-6 specifically, you would need a test that targets hexavalent chromium directly.

If chromium-6 is found, what are its possible sources in the Dover area?

Hexavalent chromium can originate geogenically, leaching from minerals in groundwater aquifers that are often alkaline and arid. Dover’s water comes from groundwater, suggesting that naturally occurring chromium-6 may be present. Industrial sources, such as chromium plating or manufacturing, also release chromium-6, but public water system data for Dover do not indicate industrial contamination patterns. Understanding the specific nature of chromium-6 presence in the local water system requires considering regional geology and potential industrial inputs.

If considering treatment, how do ion exchange and reverse osmosis differ for chromium-6?

Ion exchange targets chromium-6 by exchanging hexavalent chromium ions with other ions on a resin, potentially effective for reducing chromium-6 concentrations. Reverse osmosis uses a semipermeable membrane to filter out many contaminants, including chromium-6, but its effectiveness depends on system configuration and water chemistry. Both technologies treat chromium-6 differently, so evaluating which suits your household depends on your water’s composition, usage, and treatment goals.

If you notice issues with your water, which symptoms might relate to chromium-6?

Chromium-6 is colorless and tasteless, so typical aesthetic water quality indicators like taste, odor, or staining are unlikely to reveal its presence. Therefore, if you detect unusual tastes or smells, they may stem from other causes. Because chromium-6 lacks noticeable sensory effects at low concentrations, specific testing is essential to determine its presence and extent. Symptoms such as metallic taste do not reliably indicate chromium-6 concentration.

If your household is large, or a second or seasonal home, how does that impact chromium-6 concerns?

Water demand and usage patterns influence how treatment technologies perform over time. Larger households or properties used intermittently may experience different flow rates or storage times, affecting treatment efficiency. For example, ion exchange media may need more frequent regeneration under high use. Seasonal homes might require additional flushing due to stagnation. Considering household size and usage schedule helps tailor a chromium-6 treatment approach appropriately.

Conclusion: What not to conclude from Dover area chromium-6 data

The EPA’s public system record for Dover indicates some chromium-6 measurements above detection levels, but not above regulatory limits or health-based standards. These data describe system-wide conditions, not the specific water quality in any individual home. They do not establish whether any one household's water contains chromium-6 at any particular level. If managing chromium-6 is important for your family, the next step is to obtain a water test targeting hexavalent chromium at your point of use. The C-Series Chromium-6 Filter ships ready to configure and uses proven technology to address hexavalent chromium concerns, providing a specialized option to consider after confirming your water’s characteristics.

Where this information comes from

Source: EPA SDWIS public water system record. Sampled 2015-03-12. These figures describe the public water system's record, not the plumbing inside any individual building.

On record: EPA UCMR3 monitoring (2013-2015) for Dover Water Department (DE0000571), DE: 72 results across 2 listed contaminants, 9 detections above the reporting level; no federal MCL for hexavalent chromium; total chromium MCL 100 ug/L