Why does my water sometimes appear milky or discolored?

“Milky” or cloudy water is caused by tiny bubbles of air in the water. These bubbles do not make the water unsafe to drink, and will actually rise to the top of a glass of water if you let the water sit for a few minutes. Air can enter the pipes when a water main break is being repaired. While the Water Department tries to flush out all the air and discoloration following a break, sometimes pockets of this air get trapped in the pipes and slowly work their way out of the system, appearing as milky water. The other cause of discolored water in North Reading is iron and manganese. Iron and manganese are naturally occurring minerals that are present in the sand and gravel around the wells. As precipitation percolates down through the soil, it dissolves small amounts of iron and manganese that is then present when the Town pumps the water from the wells. Iron and manganese are not classified as health threats, and in fact the human body requires both iron and manganese (these are two of the components of most multivitamin pills). However, iron and manganese in water can cause a number of aesthetic problems, such as discoloration of the water, staining of laundry and staining of plumbing fixtures. Under the federal Safe Drinking Water Act, the EPA has established recommended limits of 0.30 mg/L for iron and 0.050 mg/L for manganese to minimize these problems. (Note – mg/L stands for milligrams per liter, which is the standard unit of measurement for many drinking water contaminants) The water drawn from the wells contains approximately 4.00 mg/L of iron and 0.800 mg/L of manganese, both well in excess of the recommended limits. North Reading treats the water from our wells to remove both iron and manganese in order to achieve a level below the recommended limits. This treatment is highly effective in reducing the iron and manganese, but it is not possible (nor practical) to remove all the iron and manganese, and the water in North Reading’s water system contains low levels of iron and manganese. The low levels of iron and manganese entering the North Reading water system from the sources do tend to settle out in the piping system before the water reaches your home, forming a very fine film of precipitated iron and manganese in the water mains. Any change in the flows in the water mains (such as when a fire hydrant is opened to fight a fire) will stir up this fine sediment and cause discolored water. This is the reason the Water Department also conducts an annual “flushing” of the water system through the fire hydrants. This scheduled change in flows helps to remove the accumulated iron and manganese in a programmed way to help minimize discolored water.