Pentair Chromium-6 Filter

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Observing Chromium-6 at Your Tap

Residents in Phoenix may notice their water meets general drinking standards without obvious issues. However, government sampling has identified varying levels of chromium-6—also known as hexavalent chromium or chromium(VI)—in the regional public water system that delivers surface water to over 1.6 million people in Maricopa County. These findings provide context but do not specify the amount in any individual household's water.

Oxidation State Changes from Source to Tap

Hexavalent chromium remains largely consistent through treatment

Chromium-6, the oxidation state where chromium is present as hexavalent chromium or Cr(VI), can persist through water distribution systems since it is relatively stable in surface waters used by Phoenix. Changes in oxidation state, such as conversion to trivalent chromium (Cr(III)), can occur but are limited within distribution mains and household plumbing.

Total chromium versus chromium-6 measurements

Government records distinguish between total chromium and chromium-6. Total chromium includes both trivalent and hexavalent forms, with regulatory limits applying only to total chromium. The sampling from 2013 to 2015 showed chromium-6 detections in almost all of 80 tested samples, with the highest detected individual concentration at 54 micrograms per liter (µg/L), equivalent to 54 parts per billion (ppb). Total chromium was similarly detected with a highest individual level recorded at 57.8 µg/L (ppb).

Implications for household water conditions

While oxidation states can shift, these data are system-wide and do not reflect individual household water chemistry changes occurring in private plumbing systems.

Sample Size and Water Sources Behind These Measurements

Scope and scale of monitoring

The data come from 80 samples collected as part of a federal occurrence survey under the Unregulated Contaminant Monitoring Rule (UCMR3) for the City of Phoenix’s public water system. This record reflects the collective sampling from surface water sources feeding the regional supply serving over 430,000 connections.

Limitations of the dataset

The number of samples provides a snapshot but does not characterize every individual connection or water condition in households. Variability naturally occurs between locations, times, and plumbing configurations, meaning exclusive reliance on system-level data cannot determine the exact chromium-6 level in your home water.

Sources of Chromium-6 in the Maricopa County Water Supply

Originates primarily from surface water collected in regional watersheds

Chromium-6 enters the supply through natural occurrences and environmental contributions captured in surface reservoirs and river sources feeding Phoenix’s water system. Industrial activities and soil mineral deposits influence its presence but are managed at the system scale through treatment processes.

Distribution system contribution

The public water distribution network itself does not generate chromium-6; rather, it transports the treated surface water to end users.

Consequences of Untreated Chromium-6 in Household Water Over Time

Potential effects on water taste and staining

Extended presence of chromium-6 in household water can contribute to taste differences or minor discoloration depending on concentration and interaction with plumbing materials. These aesthetic factors differ from health considerations and depend greatly on localized chemistry.

Understanding non-health-based implications

Long-term exposure to chromium-6 at various levels requires awareness but is not directly linked to any exceedances of federal health-based limits in Phoenix’s municipal water system record.

Aesthetic Secondary Standards Versus Health-Based Limits for Chromium-6

Distinguishing between regulatory categories

Chromium-6 is not regulated by a federal maximum contaminant level (MCL), unlike total chromium, which has a limit of 100 µg/L (ppb). The presence of chromium-6 is monitored without established health-based thresholds but may have aesthetic secondary standard considerations elsewhere, serving as guidance rather than enforceable limits.

Application to your household water decision

Awareness of aesthetic secondary standards informs concerns about taste, color, and staining but does not define safety or legal compliance.

Interpreting Certified Laboratory Test Results for Chromium-6

What a lab test reports

A certified laboratory test for hexavalent chromium quantifies its concentration in micrograms per liter (µg/L or ppb). Test reports typically show detected levels compared to reporting limits and may indicate presence without classifying risk.

How to read and use results

Interpreting chromium-6 test results involves comparing detected values with regional data and professional guidelines. Since no federal MCL exists for chromium-6, interpretation focuses on understanding the context and considering treatment based on personal tolerance or advisories.

Summary: This checklist walks through understanding chromium-6 presence in Phoenix’s regional water system from oxidation state changes to sampling scope, sources, long-term effects, standards, and lab test interpretation. With this knowledge, you can better evaluate technical options—like the Pentair Chromium-6 Filter, which ships ready to configure—for treating hexavalent chromium at your household level.

Where this information comes from

Source: EPA SDWIS public water system record. Sampled 2015-08-06. These figures describe the public water system's record, not the plumbing inside any individual building.

On record: EPA UCMR3 monitoring (2013-2015) for City of Phoenix (AZ0407025), AZ: 160 results across 2 listed contaminants, 154 detections above the reporting level; no federal MCL for hexavalent chromium; total chromium MCL 100 ug/L