Opening: What Government Sampling Shows About Chromium-6 in Pierce County Water
According to the EPA's Safe Drinking Water Information System (SDWIS), the Southwood Water System in Pierce County, WA, serving over 64,000 residents through more than 16,000 connections, has recorded chromium-6 (hexavalent chromium, chromium(VI), Cr(VI)) detections in its surface water supply. Between August 2014 and March 2015, federal monitoring found chromium-6 present in 33 of 41 samples at concentrations ranging up to 0.23 micrograms per liter (µg/L), equivalent to parts per billion (ppb). While chromium is detected, no health-based violations were noted in the water system's records.
1. How Ion Exchange and Reverse Osmosis Differ in Their Effect on Chromium(VI)
When evaluating treatment approaches following failure of existing equipment, it is helpful to understand how ion exchange and reverse osmosis address chromium(VI) presence. Ion exchange uses resin materials to exchange unwanted ions like chromium-6 for more benign ions, effectively reducing hexavalent chromium levels in water. This method typically targets specific contaminants and can handle higher flow rates relative to some alternatives.
Reverse osmosis forces water through a semipermeable membrane to separate out dissolved substances, including chromium-6 and total chromium forms. It generally achieves a broad reduction of contaminants but may produce a lower volume of treated water per unit time due to the membrane's filtering capacity.
Each technology offers distinct advantages depending on household water quality, demand, and the specific contaminant profile.
2. Why California Set a 10 µg/L Limit for Chromium-6 and Its Relevance Here
California established a public health goal for chromium-6 at 10 micrograms per liter (µg/L) or 10 parts per billion (ppb), reflecting a precautionary approach given certain toxicological studies. This threshold serves as a guideline rather than a federal enforceable standard.
Pierce County’s Southwood Water System monitoring showed chromium-6 levels well below 10 µg/L, with the highest detected at 0.23 µg/L. Thus, while California’s limit informs public awareness and treatment targets, local data indicates levels substantially below that guideline. It remains important for residents to test their own water specifically, as system-wide measurements do not define individual household quality.
3. The Significance of Sample Size and Source in Chromium-6 Measurement
The federal occurrence survey included 41 samples across the Southwood Water System’s surface water sources. Thirty-three samples detected chromium-6 above the reporting level of 0.03 µg/L, providing a median detected concentration of 0.11 µg/L.
It is important to note that these samples represent aggregated system data, not measurements from specific individual wells or household taps. The sample size offers a snapshot of the regional water supply during the monitoring period but does not reflect variations that may occur over time, location, or plumbing differences.
4. What to Document Before Seeking Treatment Advice
Before pursuing options to address chromium(VI) following equipment failure, gather detailed information to guide effective choices:
- Results of recent water tests specific to your household’s water, showing chromium-6 or total chromium concentrations
- Your household’s daily water use in gallons or liters
- Details about prior treatment equipment performance and limitations
- Any known issues with water taste, staining, or odors potentially related to chromium or other contaminants
Having these details ready will help identify suitable technologies and ensure adequate service capacity.
5. Evaluating Treatment Capacity Relative to Household Water Demand
Treatment solutions for chromium-6 such as ion exchange-based approaches should be matched to the volume of water your household consumes daily. Assess your average and peak water use and confirm the capacity of the treatment equipment to process that amount without untreated water bypass.
Understanding your usage ensures the treatment technology can maintain desired chromium-6 levels effectively and avoid operational issues.
Closing: What Not to Conclude From Area Data Alone
While government monitoring shows chromium-6 presence in the Southwood Water System at concentrations well below federal safety limits and without health-based violations, this data does not define the quality of water in any individual home or well in Pierce County. Detection of chromium-6 in system samples is not a violation or proof of unsafe water. Conversely, absence in some samples does not guarantee all household water is free from chromium(VI).
To determine if chromium-6 is a concern in your household water, direct testing of your water source is necessary. Upon confirming levels, treatment options such as the Fleck Chromium-6 Filter, which ships ready to configure, can provide control over hexavalent chromium presence tailored to your needs after existing equipment failure.
Where this information comes from
Source: EPA SDWIS public water system record. Sampled 2015-03-16. These figures describe the public water system's record, not the plumbing inside any individual building.
On record: EPA UCMR3 monitoring (2013-2015) for Southwood Water System (WA5382844), WA: 82 results across 2 listed contaminants, 49 detections above the reporting level; no federal MCL for hexavalent chromium; total chromium MCL 100 ug/L
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