Metals · CAS 7440-50-8
Copper in Tap Water
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.
Substance identity
- Scientific name
- Copper (Cu)
- Family
- Metals
- CAS number
- 7440-50-8
This guide explains the compound. Only a water-system record or household test can tell you whether it appears in your water.
- Federal reference
- Action level 1.3 mg/L (90th percentile)Enforceable maximum contaminant level
- Health-based goal
- 1.3 mg/L action level (90th percentile); MCLG of 1.3 mg/LUS EPA Lead and Copper Rule
- Measurement context
- Stated in the recordThe federal figure comes from Lead and Copper Rule 90th-percentile monitoring at household taps. A system-wide result can understate what an individual home with copper plumbing sees; a certified tap test confirms your own water. PurityMap does not yet publish a per-system measured value for Copper; this page is a reference explainer. To learn what is in your own water, check your utility’s Consumer Confidence Report (CCR) or use a certified home test.
- Cities on record
- None yetUS cities in PurityMap's published record where Copper appears
A reference is a published threshold, not a safety line drawn by PurityMap. Where a result sits against it is a finding; whether that constitutes a violation is a separately published compliance field.
What is Copper?
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.
Where Copper comes from
Corrosion of copper plumbing and brass fittings, accelerated by acidic or soft water sitting in the pipes.
- Copper household plumbing
- Brass fixtures and fittings
- Corrosive water chemistry
Most affected: Infants and people with Wilson’s disease or other copper-metabolism disorders.
How Copper is measured
The federal figure comes from Lead and Copper Rule 90th-percentile monitoring at household taps. A system-wide result can understate what an individual home with copper plumbing sees; a certified tap test confirms your own water. PurityMap does not yet publish a per-system measured value for Copper; this page is a reference explainer. To learn what is in your own water, check your utility’s Consumer Confidence Report (CCR) or use a certified home test.
Why context mattersHow PurityMap reads a Copper result
Evidence exceeds a reference level. Used sparingly and only when warranted.
This substance was found in the monitoring record. Being present is not the same as being above a reference level, and this signal does not say which.
Somebody looked and the laboratory reported nothing above its reporting limit. This is a result, and it is not the same as nobody looking.
No sampling for this substance has been reported for this system. Nothing is known either way, and an empty row is not a clean one.
Where the numbers come from
- A laboratory result for one sampling point
Collected under a monitoring programme, analysed by an approved method, and reported with its own detection limits.
- Read against a published reference
The reference comes from the regulator, with its own effective date. PurityMap does not set thresholds and does not adjust them.
- Attached to a system's Water Profile
Where it contributes to the published assessment alongside the evidence quality of the record it came from.
The full evidence chain →
Where Copper is found across the U.S.
These are the places in PurityMap’s published record where Copper appears on a water system’s monitoring results. It reflects the systems and sampling we track, not a national prevalence estimate.
PurityMap has no city on record with Copper on its monitoring results yet. This fills in as monitoring data is published — a substance that was never tested is shown as pending, never as a pass.
Treatment capability, if a finding establishes a need
The formats that commonly hold a verified reduction claim for Copper are Reverse osmosis, Corrosion Control / pH adjustment, Flushing standing water before use. Holding the format is not holding the claim — the certification record is what is checked.
Boiling does not remove a dissolved chemical compound and can concentrate it. Many pitcher and refrigerator filters carry no verified claim for a compound like this at all.
Whether a system-level measurement or a household-tap measurement is the relevant scope depends on how the compound enters the water — a published characteristic of the record, not an assumption drawn here.
A finding establishes the need, the need names the capability, the capability requires a verified certification. No product appears before that sequence completes.
Filter Finder →Frequently asked questions
What is Copper?
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.
What is the limit for Copper in drinking water?
The enforceable federal limit is Action level 1.3 mg/L (90th percentile). The health-based goal is 1.3 mg/L action level (90th percentile); MCLG of 1.3 mg/L. PurityMap reads every measurement against its stated benchmark and never sets its own.
Where does Copper in tap water come from?
Copper household plumbing, Brass fixtures and fittings, Corrosive water chemistry.
Why does Copper matter?
Short-term exposure to elevated copper can cause gastrointestinal upset; long-term exposure above the action level is associated with liver and kidney effects, and is a particular concern for people who cannot regulate copper. Because copper is usually added at the tap, a first-draw sample after water has sat overnight tends to read highest.
How do you remove Copper from water?
Treatment technologies commonly certified to reduce Copper include Reverse osmosis, Corrosion-control / pH adjustment, Flushing standing water before use. Match the exact certified claim to your water before buying — holding a format is not the same as holding the claim.
Sources and methodology
Reference values on this page come from the governed contaminant record. Local occurrence claims stay on the linked water-system evidence pages, where sampling scope, period and source remain visible.
How PurityMap analyzes water data →