Does chromium-6 change between the well, the distribution main, and your tap?
Chromium in water can exist in different oxidation states, primarily trivalent chromium (Cr(III)) and hexavalent chromium (Cr(VI), also known as chromium-6). The chemical form can transform depending on environmental conditions such as oxygen levels and the treatment processes in water systems. Groundwater often contains chromium in one form or another, but changes can occur as water moves into the distribution system and your home. In Kitsap County’s Silverdale Water District, which relies on groundwater, federal monitoring showed chromium-6 detected in many samples but did not establish the exact state changes within the distribution network or at individual taps. To know your tap water’s chromium speciation, a specific test of your household water is necessary.
Why can’t total chromium results alone answer chromium-6 concerns?
Total chromium measurements combine all chromium forms without distinguishing Cr(VI) from Cr(III). This differentiation matters because the properties and health-related considerations vary between these forms. In Kitsap County’s Silverdale Water District, tests found total chromium detected in most samples with values up to 10.0 micrograms per liter (µg/L or parts per billion, ppb) and chromium-6 up to 9.9 µg/L. Since total chromium includes multiple species, a total chromium number cannot specify how much chromium-6 is present; a separate chromium-6 test is required for that information.
What steps should you take to understand chromium levels at home?
If existing equipment addressing chromium-6 has failed, start with these steps to clarify your household water conditions:
- Check your water provider’s recent water quality reports to understand system-wide data such as the Silverdale Water District’s federal monitoring.
- Consider low-cost checks for related water parameters that may indicate water chemistry changes affecting chromium forms.
- Obtain a laboratory test specifically analyzing chromium-6 in your household water to assess your unique situation since system data cannot substitute for this.
This approach helps prioritize actions before investing in water treatment solutions.
Why do aesthetic secondary standards differ from health-based limits for chromium?
Secondary standards primarily address taste, staining, and corrosion issues, not health risks. For chromium, EPA’s federal records for the Silverdale Water District show no health-based violations, reflecting water meets health protection criteria. However, aesthetic concerns might still arise at chromium concentrations below or near secondary guidelines. Understanding this distinction clarifies that detection above a certain level is not a health violation but may relate to water quality perception. Hence, managing chromium-6 involves considering both health-based information and household aesthetic preferences.
How does chromium concentration vary seasonally or over multiple years in Kitsap County?
Monitoring in Silverdale Water District between 2014 and 2015 showed chromium-6 detections in 38 of 44 samples, with a highest measured level of 9.9 µg/L and a median of 5.8 µg/L. These measurements represent a snapshot across months and do not indicate a fixed number but rather a range observed over time. Chromium concentrations can fluctuate seasonally due to changes in groundwater chemistry and environmental factors. Recognizing this variability supports ongoing monitoring for those concerned about chromium-6 in their water.
What should you NOT conclude from this area’s data?
The presence of chromium-6 detections in the Silverdale Water District’s public water system record does not mean your household’s water has the same levels or that the water is unsafe. No health-based violations were recorded for chromium by EPA for this system. Only a direct laboratory test of your own water will determine specific chromium-6 levels at your tap. If your existing equipment for chromium-6 is no longer effective, consider a replacement option like the C-Series Chromium-6 Filter, which ships ready to configure and is documented to address chromium-6 concerns effectively.
Where this information comes from
Source: EPA SDWIS public water system record. Sampled 2015-06-29. These figures describe the public water system's record, not the plumbing inside any individual building.
On record: EPA UCMR3 monitoring (2013-2015) for Silverdale Water District #16 (WA5379300), WA: 88 results across 2 listed contaminants, 78 detections above the reporting level; no federal MCL for hexavalent chromium; total chromium MCL 100 ug/L