Trivalent versus Hexavalent Chromium: Why Total Chromium Does Not Tell the Whole Story
Different forms of chromium have different properties
Hexavalent chromium (chromium-6 or Cr(VI)) and trivalent chromium (chromium-3) are distinct chemical forms. Total chromium reported in water tests combines both types but does not specify how much chromium-6 is present. Therefore, seeing a total chromium figure alone does not reveal the chromium-6 level.
Regulatory monitoring targets chromium-6 separately
Because chromium-6 has different characteristics and potential concerns, specific measurements are taken in surveys such as the EPA’s Unregulated Contaminant Monitoring Rule (UCMR3). This helps understand chromium-6 presence independently of total chromium.
What the UCMR3 Nationwide Survey Means and Its Limits for a Single Household
Data reflects system-wide public water sampling
Between 2013 and 2015, the EPA monitored chromium-6 levels in the Pierre public water system serving Hughes County. Among 26 samples, only one measured chromium-6 slightly above the 0.03 micrograms per liter (µg/L) reporting level, at 0.032 µg/L (equivalent to parts per billion, ppb). Total chromium showed a highest level of 0.2 µg/L. These are not violations but detections within a federal occurrence study.
Individual household water quality can differ
Because this data represents public system measurements, it does not specify water quality at any single household tap. Factors such as plumbing materials, water treatment devices, and well water sources (if applicable) can alter chromium levels locally. Testing your own water is necessary to confirm household presence.
Household Symptoms That May or May Not Indicate Chromium-6 Presence
Chromium-6 is not detectable by taste or odor
No sensory symptoms like taste, smell, or color changes reliably indicate chromium-6 presence. Detecting it requires laboratory analysis due to its low concentration levels.
Equipment performance can affect water quality concerns
If existing water treatment devices have ceased functioning properly, chromium-6 or other substances may reappear or increase. However, symptoms such as staining or corrosion may relate to other water constituents, not chromium-6 specifically.
Influence of Plumbing Materials and Age on Chromium Levels
Older plumbing can impact water chemistry
Metal pipes and fixtures may interact with water, sometimes leading to changes in trace element concentrations. This interaction is separate from source water chromium levels and can alter water at the tap.
Surface water source does not guarantee uniform chemistry throughout
The Pierre public water system draws from surface water, which undergoes treatment before distribution, but household plumbing remains a variable for final water composition.
Comparing Ion Exchange and Reverse Osmosis Technologies for Chromium(VI)
Ion exchange targets specific ions like chromium-6
Ion exchange units chemically bind hexavalent chromium ions, reducing chromium-6 concentrations effectively. This method can be tailored to household needs but depends on device condition to maintain efficiency.
Reverse osmosis provides broad filtration
Reverse osmosis membranes filter dissolved solids including chromium-6 by forcing water through a semipermeable barrier. It also removes other minerals and contaminants but requires proper maintenance for sustained results.
Summary and Next Steps
The EPA’s public water system records from 2013 to 2015 for Pierre, Hughes County, show minimal chromium-6 detections at levels slightly above the reporting limit but well below any federal maximum contaminant level. This data applies to the public water system overall, not individual homes. To determine chromium-6 presence in your household water, especially after water treatment equipment failure, testing your water at a certified laboratory is necessary. For managing chromium-6, the C-Series Chromium-6 Filter ships ready to configure and can address chromium(VI) through proven technologies such as ion exchange.
Information source: EPA SDWIS public water system records for Pierre (SD4600242).
Where this information comes from
Source: EPA SDWIS public water system record. Sampled 2015-06-09. These figures describe the public water system's record, not the plumbing inside any individual building.
On record: EPA UCMR3 monitoring (2013-2015) for Pierre (SD4600242), SD: 52 results across 2 listed contaminants, 2 detections above the reporting level; no federal MCL for hexavalent chromium; total chromium MCL 100 ug/L