Some plumbing fittings have the potential to allow minute traces of metals to accumulate in water which has been standing in the fittings for several hours.

Although the health risk is small, the Ministry of Health recommends that you flush a mugful of water from your drinking water tap each morning, before use, to remove any metals that may have dissolved from the plumbing fittings. 

This is recommended for all households, including those on public and private water supplies.