Copper

Copper

Copper is a metallic chemical element with a distinctive pinkish colour, and is one of the few metals to occur naturally in its native form, so was used from about 8,000 BC onwards, both as a native metal, and in alloys such as bronze and brass, as it is easily worked with a relatively low melting point. Historically ships had copper cladding because the metal is biostatic, preventing fouling.

Today, copper is used extensively for electrical wiring, and electrical motors and as a building material because of its good electrical and thermal conductivity. Copper roofing develops a distinctive green colour by forming Verdigris, and copper salts are used as fungicides (Bordeaux mixture) and wood preservatives, as well as pigments. Copper has long been used in plumbing as it is easily formed and bent, and can be easily soldered to make watertight joints. It is also used extensively in heat exchangers.

Copper has good resistance to corrosion at neutral pH because the native metal is protected by a thin layer of copper oxide but can be subject to galvanic corrosion if placed next to a dissimilar metal such as iron, when copper salts may be released into solution and acidic water will increase corrosion, especially in the hot water system.

Agency Limit (ppm)
UK - DEFRA 2
US - EPA 1.3
EU - EEA 2
WHO 2

Copper and our health

Copper is an essential trace dietary mineral as it is a key constituent of the respiratory complex cytochrome C oxidase, and is also part of the oxygen carrying haemocyanin, in molluscs and Crustacea, (replaced by haemoglobin in fish and higher organisms). Humans contain 1.5 to 2.1mg copper per kilogram of body weight.

Copper in our drinking water

The RDA for copper in adults is 900ug, and this will come from both food and water supplies. High levels of copper in drinking water can impart a metallic taste and are toxic, especially to infants and to adults with defects in copper metabolism. Toxic amounts of copper can cause vomiting, headache and diarrhoea. The upper limit for copper in drinking water is set at 1.3 mg/litre, and most domestic supplies are well under this limit, but high levels can result if acidic water is left standing in pipes, or if hot water is used for cooking.. After water has stood in pipes, it is advisable to draw off the first few litres before using it for drinking or cooking. High levels of copper can also discolour clothes during laundry, and can impart a green colour to your hair, as well as leaving green or blue residue in baths and washbasins.

Tests

Copper in your drinking water can be detected by the following tests.

Removing Copper

Copper can be reduced or removed from your drinking water using the following methods.

  • Reverse Osmosis
  • Cation Exchange Columns
  • Activated Carbon Filters

Further reading