A new study commissioned by UK Water Industry Research (UKWIR) and conducted by the University of Sheffield has revealed important insights into the behavior of deteriorating grey cast iron (GCI) pipes. The research, detailed in the recently released report ‘Understanding how the deterioration of cast iron pipes evolves into leakage’, shows that micro-cracks in these pipes can temporarily 'reseal' themselves when water pressure is lowered, providing a valuable tool for managing leaks in the UK's aging water infrastructure.
Grey cast iron pipes, many of which date back to the interwar period, have long been a challenge for the UK water industry. These pipes are particularly vulnerable to corrosion, leading to cracks and leaks over time. As part of the effort to reduce leakage, UKWIR sought to better understand the failure mechanisms behind these pipes, especially in response to pressure changes within the water distribution system.
Jeremy Heath, innovation manager at SES Water and program lead for UKWIR’s Big Question 2, explained, “The data revealed that under certain dynamic loads, micro-cracks in the pipe can reseal if the loading is reduced. This occurs because the residual strength of the cast iron pulls the crack shut, temporarily halting the leak.” This discovery gives utilities an opportunity to better prioritize pipe replacements, extending the life of their systems and reducing the frequency of disruptive leaks.
Grey cast iron pipes, many of which date back to the interwar period, have long been a challenge for the UK water industry
The study used a combination of physical and numerical experiments to understand how leaks form in GCI pipes. Destructive laboratory tests were conducted on pipes with artificial corrosion pits, simulating the conditions that lead to failure. Researchers applied internal water pressure and bending loads to see how they affected the pipe’s strength, with high-speed cameras capturing how cracks developed under different conditions. The findings highlighted the significant role of pressure transients, sudden pressure changes that occur during events like pump operations or valve closures—on the pipe’s fatigue and failure processes.
The results suggest that reducing maximum stress through careful pressure management can prevent or delay the formation of larger leaks. This discovery opens the door for water companies to better assess their networks and make more informed decisions about where to replace or repair pipes. Mike Rose, CEO of UKWIR, emphasised the importance of this collaborative research, saying, “This project perfectly illustrates our mission to provide one voice for the shared issues facing water operators today. It not only advances our understanding of leakage but also helps to extend the life of water company assets.”
The research also highlights the need for improved monitoring of the condition of GCI pipes. By tracking the development of small leaks and understanding when they may reseal, utilities can avoid unnecessary disruptions and focus their resources more effectively. Ultimately, these findings align with UKWIR’s long-term goal of reducing water leakage to zero by 2050, enabling utilities to take a more proactive approach to managing their infrastructure.
