Trivalent versus Hexavalent Chromium: Why Total Chromium Data Alone Is Insufficient
Residents in Exeter often see reported figures for both total chromium and chromium-6 in local water quality data. Total chromium encompasses all chromium oxidation states present, but the specific form chromium-6 (or hexavalent chromium, Cr(VI)) influences treatment selection differently due to its chemical properties. While the public water system record includes total chromium levels, these do not directly represent the concentration of chromium-6, which is of unique interest when choosing appropriate home water treatment equipment.
How Chromium’s Oxidation State Can Change Between Source, Distribution, and Tap
The oxidation state of chromium may shift as water moves from Exeter’s surface water source through treatment and distribution. Chromium-6 can transform into chromium-3 (trivalent chromium), altering its reactivity and behavior in the water. This chemical transformation means that chromium-6 concentrations measured at the water source or distribution system may differ from what exits household taps.
Interpreting "Detected," "Median," and "Range" in Government Sampling Records
EPA monitoring of Exeter’s water system from 2013 to 2015 found chromium-6 detected in 6 of 16 samples above a reporting level of 0.03 micrograms per liter (µg/L), with the highest measured value at 0.046 µg/L and a median of detected values at 0.035 µg/L. The term "detected" means the instrument measured chromium-6 above the threshold for reporting, not that the water is unsafe. These values are parts per billion (ppb), the same units expressed differently. It’s important to recognize that these figures represent system-wide data, not the specific water at any one home.
Distinguishing Chromium-6 Issues from Commonly Confused Water Concerns
Chromium-6 should not be confused with other water quality variables like total dissolved solids or other metals. It is distinct in its oxidation state and related effects. Unlike contaminants governed by strict maximum contaminant levels (MCLs), chromium-6 currently lacks a federal MCL, and the total chromium MCL of 100 µg/L reported by EPA does not restrict chromium-6 specifically. This makes understanding the particular form of chromium present critical in assessing treatment needs.
Steps to Rule Out Alternative Causes Before Considering Chromium-6 Treatment Options
Homeowners should start with evaluating common household water quality parameters and equipment conditions that might impact water taste, appearance, or appliance performance before focusing on chromium-6 treatment. Simple checks include assessing water color, odor, or staining issues, and confirming test results with a laboratory analysis specifically targeting chromium-6 to ascertain its concentration at the tap.
How Public Water System Records Differ from Private Well Testing
The Exeter Water Department’s public system record offers area-wide monitoring data based on multiple samples from the entire distribution system. This broad snapshot helps identify trends but cannot determine chromium-6 levels in any single household’s water. In contrast, individual well testing provides direct information about your specific water, necessary to personalize treatment decisions.
What You Should NOT Conclude from Area-Level Chromium-6 Data
Area data showing chromium-6 detections at low levels does not imply your household water contains the same concentrations or that it is unsafe. The absence of a federal chromium-6 MCL means government monitoring documents occurrence but does not label these measurements as violations or health risks. To determine whether specific water treatment equipment suits your needs, confirm your home's chromium-6 concentration through laboratory testing. The Fleck Chromium-6 Filter ships ready to configure and offers a reliable equipment option documented to address chromium-6 concerns once your water profile is established.
Where this information comes from
Source: EPA SDWIS public water system record. Sampled 2014-03-04. These figures describe the public water system's record, not the plumbing inside any individual building.
On record: EPA UCMR3 monitoring (2013-2015) for Exeter Water Department (NH0801010), NH: 32 results across 2 listed contaminants, 8 detections above the reporting level; no federal MCL for hexavalent chromium; total chromium MCL 100 ug/L