Researchers found that washing with water containing the metal from copper pipes can lead to split ends and unmanageable hair.
They found the metal gradually builds up in hair, helping to speed up damage caused by sunlight, causing split ends, fly-away strands and less shine, The Telegraph reported.
The effect is even more pronounced in those who use hair dyes, researchers claim.
"Copper is not present in large amounts but it is important as it is catalytically active. The copper comes in from the tap water and the hair acts like a sponge picking it up over time," said Dr Jennifer Marsh, a research fellow at Proctor and Gamble who led the research.
"Physical processes like brushing, blow drying and washing, hair is less able to stand up to those and it will break down faster and lead to split ends, lack of shine and make it harder to manage," she said.
Marsh and her colleagues analysed hair from 450 women from around the world and found that they had varying levels of copper in their hair.
Low levels of copper in drinking water are thought to occur naturally while purifying processes used by water companies can add more.
Most copper, however, comes from traditional copper pipes used in British houses. Even in homes with plastic piping, hot water tanks can be made from copper.
As a single strand of hair can grow for up to three years before falling out, the low levels of the metal in the water can build up in the outer layers of the hair, the researchers found.
This strips hair strands of their shine and leaves them weaker than normal, meaning they are more prone to breaking when brushing or to damage from blow drying.
The researchers also found that treating hair with chemicals more commonly used in washing powder, known as chelants, could reduce the action of the copper.
The findings were published in the International Journal of Cosmetic Science.
