Understanding the Corrosion Factors of Cast Iron Mains

The overall project aim is to understand how water chemistry can be adjusted to reduce corrosion rates and stabilise the corrosion already apparent in our mains. To achieve this, the following objectives are set:
- Understand the effect of pH, hardness, alkalinity and chloride levels on corrosion rates in soft water.
- Understand if adjusting orthophosphate concentration can aid in preventing corrosion.
- Investigate potential additions to water treatment to ascertain if corrosion can be prevented or stabilised.
- Ascertain the cost benefit of suitable measures to prevent corrosion.
- Involvement in a pilot of successful treatment options.

Welsh Water is proud to provide essential public services in the management of the water cycle to over three million people across most of Wales and some adjacent parts of England. 40% of Welsh Water's mains (11,000km of the 27,500km) are cast iron. Over time these cast iron mains corrode causing discolouration to our customers. Corrosion rates are dependent on the chemistry of the water passing through these mains. By understanding how water chemistry effects corrosion rates and the stabilisation of mains that already are corroded, Welsh Water will be able to reduce customer complaints about discoloured water.