Copper
What is Copper?
Copper mostly enters drinking water the same way lead often does: not from the source, but by leaching from copper pipes, brass fittings, and fixtures as water sits in your home's plumbing. Corrosive or acidic water and long standing time raise how much dissolves in.
Health effects
Small amounts of copper are an essential nutrient, but higher levels in drinking water can cause short-term stomach upset, nausea, and cramps, and long-term exposure can affect the liver and kidneys. People with Wilson's disease, an inherited condition, are especially sensitive. The EPA sets an action level of 1.3 mg/L and a secondary (taste and staining) standard of 1.0 mg/L.
In DC-metro tap water
Because copper comes from plumbing rather than the source, levels vary from one home to the next, and are highest in houses with copper pipes, in new plumbing that hasn't yet 'seasoned,' and where corrosive water sits overnight. A blue-green stain on sinks or fixtures is a common visible sign.
How to remove it at the tap
Flushing the tap after water has been sitting reduces copper temporarily, but the reliable fix is point-of-use treatment. A reverse osmosis system reduces dissolved copper at the tap, along with other plumbing metals like lead.
Frequently asked
Why is there copper in my tap water?
Almost always from your own plumbing: copper pipes and brass fixtures leach small amounts of copper into water, especially when the water is corrosive or has been sitting in the pipes.
Is copper in water bad for you?
Trace copper is essential, but higher levels can cause stomach upset short-term and liver or kidney effects long-term, with people who have Wilson's disease most at risk. That's why the EPA sets an action level of 1.3 mg/L.
Does reverse osmosis remove copper?
Yes. Reverse osmosis reduces dissolved copper at the point of use, along with other metals that leach from plumbing.