FAQs - Details

Why does the Edinburgh Water utilities flush water mains ?

Flushing helps maintain water quality. The water entering distribution mains is of very high quality; however , water quality can deteriorate in distribution mains if the mains are not properly managed. This is why flushing is important. Flushing maintains water quality in several ways. First, flushing removes sediments from the mains. These sediments mostly include iron and manganese. Iron sediment results from corrosion of iron pipes and valves used in the distribution system. Other iron sediments result from the change of dissolved iron, which occurs naturally in our water, into sediment form. This occurs in the presence of chlorine and oxygen under certain low flow conditions. Dissolved manganese also occurs naturally in our water and it can be changed into sediments as with iron. Although iron and manganese do not pose health concerns, they can degrade the " acceptability " of the water through affecting the taste, clarity, and color of the water. In addition, sediments can shield micro-organisms from the disinfecting power of chlorine. Therefore, such sediments could contribute to the growth of micro-organisms within distribution mains. Finally, flushing helps remove " stale " water. Much of our distribution is designed with " loops " or interconnected grids, which keep water constantly moving around. However, some areas have dead-ends where water moves slowly and sits for longer periods of time. Such dead-end mains need to be flushed to ensure the presence of fresh water with sufficient dissolved oxygen, disinfectant levels and an acceptable taste and smell.