Copper in Drinking Water
How Copper Gets Into Water
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Copper is a mineral and natural component of soils. It is an essential nutrient for humans and plants.
Industrial pollution, domestic wastewater, mining wastewater, and
weathering of copper-bearing rocks are major sources of copper in
surface and ground waters. Discharges of copper into sewer systems from
some residential areas have also been found.
Leading areas of use for copper and its alloys are the plumbing,
electrical, and electronic industries. Copper compounds are used as
agricultural fungicides, algaecides in water reservoirs, in food
supplements, and fertilizers.
In Washington, most copper in drinking water comes from corrosion of
household plumbing. Public water supplies are required to conduct
treatment to reduce corrosion when more than 10 percent of the tap water
samples exceed 1.3 parts per million (ppm) of copper.
Copper from plumbing corrosion can accumulate overnight. Flushing the
water from the tap for 30 to 45 seconds can reduce the copper that can
accumulate when the household plumbing is not in use.
Health Issues
Copper is an essential mineral in the diet. Too much copper, however,
can cause health problems. Major food sources of copper are shellfish,
nuts, grains, leafy vegetables, and stone fruits. Typical sources of
copper from food range from less than 2 milligrams (mg.) to 5 mg. per
day.
Health studies have found that copper in drinking water can add 4 to 45
percent more copper to a person’s diet than what is in food sources.
Absorption studies have indicated that the body excretes about half of
ingested copper, which offers some protection against copper poisoning.
Copper is widely distributed within the tissues of the body, but
accumulates primarily in the liver and kidneys.
The National Academy of Science recommends 2-3 mg of copper in the
daily diet. A single dose of 15 mg of copper can cause nausea, vomiting,
diarrhea, and intestinal cramps. Severe cases of copper poisoning have
led to anemia and to the disruption of liver and kidney functions.
Individuals with Wilson’s and Menke’s diseases (genetic disorders
resulting in abnormal copper absorption and metabolism) are at higher
risk from copper exposure than the general public, and can have serious
health problems.
Detecting Copper in Drinking Water
Blue-green stains on plumbing fixtures are usually an indication of
the presence of copper in drinking water. Some factors that affect
copper levels in household drinking water are:
- Acidic water (low pH)
- Soft water (low in calcium and magnesium)
- High chlorine residual levels
- Long standing time in pipes
- Elevated water temperature
Backflow Prevention for Carbonated Beverage Dispensers
There is a great risk of copper contamination from carbonated or
acidic beverages that have been in contact with copper tubing, fixtures,
or containers. The carbon dioxide used in soft drink dispensers is under
pressure. Where it is mixed with the incoming water, there is a
potential for carbon dioxide to backflow through the incoming water
supply. The carbon dioxide then can corrode copper plumbing, which can
add copper to soft drinks. The surest way to prevent the carbon dioxide
from contacting copper plumbing pipes is to install a reduced pressure
backflow prevention assembly (RPBA). This assembly should be installed
on the incoming water supply pipe before the carbon dioxide injection
point. Copper piping should not be used past the injection point. (Some
utilities may allow the substitution of a dual-check valve with an
intermediate vent in place of the RPBA).
For More Information
Office of Drinking Water Regional Offices
General Information: 1-800-521-0323
Southwest Region (360) 236-3030
Northwest Region (253) 395-6750
Eastern Region (509) 329-2100
After-hours (877) 481-4901
January 2006
DOH PUB. #331-178
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