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Contaminant family guide

Metals in Tap Water

Metals in drinking water can originate in source water, treatment processes, or plumbing. The compound, form, sampling location, and unit all matter.

Check my local water

9 compound guides6 with a federal MCL15 treatment methods named

What are metals?

A family label, not a compound

This family groups metallic elements and related analytes that appear in drinking-water records. Their behavior and health context vary, so family membership alone does not establish risk.

Some metals are regulated at the treatment system while others, including lead and copper, are strongly shaped by premise plumbing and tap-sampling protocols. Local evidence must preserve that scope. The lead action level is a treatment trigger, not a health-based limit: public-health agencies state there is no known safe level of lead exposure.

Sources named in the compound records
  • Lead service lines
  • Lead solder
  • Brass fixtures
  • Natural mineral deposits
  • Mining and smelting
  • Legacy agricultural chemicals
  • Industrial / metal-plating discharge
  • Natural geological deposits
Published compound guides

Nine published compound guides

Eight have a federal limit; the rest carry the context their record states.

Cities where lead exceeds the federal action level →
CAS 7439-92-1LeadLead (Pb)Lead is a toxic metal that usually enters drinking water from corrosion of lead service lines, solder, and household plumbing rather than from the source water.15 µg/LAction level90th percentile · MCLG 0 · A treatment trigger, not an MCLRead compound evidence →CAS 7440-38-2ArsenicArsenic (As)Arsenic is a naturally occurring semi-metal that dissolves into groundwater from rock and soil, and can also enter water from mining and legacy agricultural chemicals.10 µg/LMCLMCLG 0Read compound evidence →CAS 18540-29-9Chromium-6Hexavalent chromium (Cr-VI)Hexavalent chromium (chromium-6) is a form of chromium from industrial processes and some natural deposits, the contaminant made famous by the Erin Brockovich case.NoneNo federal limitNo separate federal MCL; total chromium MCL is 100 µg/LRead compound evidence →CAS 7440-50-8CopperCopper (Cu)Copper is a metal that usually enters drinking water from the corrosion of household copper pipes and brass fixtures rather than from the source water. Small amounts are an essential nutrient; the concern is elevated levels.1.3 mg/LAction level90th percentile · MCLG 1.3 mg/L · A treatment trigger, not an MCLRead compound evidence →CAS 7440-39-3BariumBarium (Ba)Barium is a metal that enters drinking water mostly through the natural erosion of mineral deposits, and sometimes from industrial discharge or oil-and-gas activity.2 mg/LMCLMCLG 2 mg/LRead compound evidence →CAS 7782-49-2SeleniumSelenium (Se)Selenium is a trace element that is an essential nutrient in tiny amounts but is regulated in drinking water because higher levels from natural deposits or runoff can be harmful.50 µg/LMCLMCLG 0.05 mg/LRead compound evidence →CAS 7440-43-9CadmiumCadmium (Cd)Cadmium is a toxic metal that can enter water from the corrosion of galvanized pipes and from industrial discharge, mining, and runoff.5 µg/LMCLMCLG 5 µg/LRead compound evidence →CAS 7439-97-6MercuryInorganic mercury (Hg)Inorganic mercury is a toxic metal that reaches water from natural deposits, industrial discharge, and runoff. The drinking-water rule addresses inorganic mercury, distinct from the methylmercury that builds up in fish.2 µg/LMCLMCLG 2 µg/LRead compound evidence →CAS 7440-36-0AntimonyAntimony (Sb)Antimony is a metal that can enter drinking water from natural deposits and from discharge related to petroleum refineries, fire retardants, ceramics, and electronics.6 µg/LMCLMCLG 6 µg/LRead compound evidence →
How to read a local result

Four checks before you act

  1. STEP 1Identify the named analyte

    A family name may contain compounds with different standards and health contexts.

  2. STEP 2Keep the measurement attached

    Read the value with its unit, qualifier, sampling period, reporting limit and source.

  3. STEP 3Compare only with the stated reference

    PurityMap does not turn unlike compound results into a family score or safety verdict.

  4. STEP 4Verify the treatment claim

    The product certification must name the compound or reduction claim.

Treatment capabilities in the published records

15 methods, each named by the compound guides

A technology name is only a starting point. Confirm the product’s certification names the compound before choosing equipment.

Choosing a lead water filter
  • Reverse osmosis

    Named by 9 of 9 compound guides in this family.

    PbAsCr⁶⁺CuBaSeCdHgSb
  • Anion exchange

    Named by 3 of 9 compound guides in this family.

    AsCr⁶⁺Se
  • Coagulation / filtration

    Named by 2 of 9 compound guides in this family.

    HgSb
  • Activated alumina

    Named by 1 of 9 compound guides in this family.

    Se
  • Activated alumina / adsorptive media

    Named by 1 of 9 compound guides in this family.

    As
  • Activated carbon (GAC)

    Named by 1 of 9 compound guides in this family.

    Hg
  • Activated carbon (some configurations)

    Named by 1 of 9 compound guides in this family.

    Cd
  • Corrosion-control / pH adjustment

    Named by 1 of 9 compound guides in this family.

    Cu
  • Electrodialysis

    Named by 1 of 9 compound guides in this family.

    Ba
  • Flushing standing water before use

    Named by 1 of 9 compound guides in this family.

    Cu
  • Ion exchange

    Named by 1 of 9 compound guides in this family.

    Cd
  • Ion exchange (softening)

    Named by 1 of 9 compound guides in this family.

    Ba
  • NSF/ANSI 53 lead-certified filters

    Named by 1 of 9 compound guides in this family.

    Pb
  • Reduction / filtration systems

    Named by 1 of 9 compound guides in this family.

    Cr⁶⁺
  • Replacing lead service lines

    Named by 1 of 9 compound guides in this family.

    Pb
Related intelligenceAssembled from PurityMap’s governed contaminant records. How we analyze water data
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