Is it safe to drink water stored overnight in a copper container?

Safety of Drinking Water Stored Overnight in Copper Containers

Copper containers should not be used to store water overnight or prepare drinks, as this practice can lead to excessive copper leaching and potential toxicity. 1

Direct Guideline Recommendation

The Hepatology guidelines explicitly state that "copper containers or cookware should not be used to store or prepare foods or drinks." 1 This recommendation comes from authoritative guidelines on Wilson disease management published in Hepatology (2008), which address copper exposure comprehensively.

Why This Matters: Copper Leaching and Toxicity Risk

Copper Leaching from Containers

• Water stored overnight in copper containers can leach copper into the water, with concentrations potentially reaching 475 parts per billion (ppb) or higher. 2
• While 475 ppb is technically below WHO safety limits for drinking water (2.0 mg/L = 2000 ppb), this represents a single exposure source that adds to total daily copper intake from food and other sources. 2, 3
• The actual amount leached varies based on water chemistry, storage duration, and container condition, making exposure unpredictable. 1

Toxicity Concerns

Acute gastrointestinal symptoms can occur even at copper concentrations below regulatory limits:

• Nausea, vomiting, abdominal colic, and diarrhea are the primary manifestations of copper-induced gastrointestinal toxicity. 4
• In infants, symptoms include formula refusal, persistent restlessness, unexplained screaming (especially at night), and prolonged diaper rash. 4
• These symptoms can occur with chronic exposure to copper in drinking water, even when concentrations are within "acceptable" regulatory ranges. 4

Systemic toxicity with prolonged exposure includes:

• Elevated "free" (non-ceruloplasmin-bound) copper in serum, which is the toxic form. 5
• Liver damage progressing to cirrhosis in severe cases. 5, 4
• Hematemesis, hypotension, melena, and cardiovascular collapse in acute severe toxicity. 1, 6
• Neurological dysfunction and potential multi-organ failure. 6

Safe Copper Intake Limits

• The no-observed-adverse-effect level (NOAEL) is 10 mg/day for chronic copper exposure in adults. 1, 7
• Daily dietary intake recommendations are 1.1-2.0 mg/day for adults, with typical Western diets providing copper in the lower range. 1
• Water stored in copper containers adds an uncontrolled variable to total copper intake, potentially pushing exposure toward or beyond safe limits. 1

High-Risk Populations Who Must Avoid Copper Containers

Individuals with Wilson disease (genetic copper metabolism disorder):

• These patients cannot excrete copper normally and accumulate it in the liver, brain, and other organs. 1
• Any additional copper exposure is contraindicated and potentially life-threatening. 1

Patients with cholestatic liver disease or hepatic dysfunction:

• Impaired biliary copper excretion leads to copper accumulation and toxicity. 1
• These individuals require copper restriction, not supplementation. 1

Infants and young children:

• More susceptible to copper toxicity with lower tolerance thresholds. 5, 4
• Symptoms may be subtle (irritability, feeding difficulties) and easily missed. 4

Practical Recommendations

For water storage:

• Use glass, stainless steel, or food-grade plastic containers instead of copper. 1
• If you have copper plumbing, flush stagnant water before using it for drinking or cooking. 1
• Consider testing your water supply if copper pipes are present and water has high acidity or low mineral content (which increases copper leaching). 1

If copper container use is suspected as a cause of symptoms:

• Discontinue use immediately if experiencing gastrointestinal symptoms (nausea, vomiting, abdominal pain, diarrhea). 4
• Measure serum copper (total and non-ceruloplasmin-bound), ceruloplasmin, and 24-hour urinary copper excretion. 1, 5
• Normal urinary copper is <15 mcg/dL in adults; elevated levels (>15 mcg/dL) suggest copper overload. 5
• Free serum copper should be <0.3 micromol/L (or <1.6% of total serum copper); levels of 5.1-47.1 micromol/L indicate toxicity. 5

Important Caveats

The antimicrobial claims for copper water storage are not a justification for use:

• While copper does have antimicrobial properties and can kill enteric bacteria in water, 2 this does not outweigh the toxicity risks from chronic copper exposure.
• Modern water treatment and safe storage practices are preferable to relying on copper's antimicrobial effects. 2

Regulatory limits may not protect everyone:

• Cases of chronic copper poisoning have occurred at concentrations below regulatory guidelines. 4
• Individual susceptibility varies, and cumulative exposure from multiple sources (food, water, cookware) must be considered. 1, 4