WET News

18 WET NEWS APRIL 2016 Leakage levels may have fallen, but pressure fluctuations can create more bursts and aggravate existing leaks further. i2O's Keith Hilson explains. The challenge: Leakage is the symptom, not the cause INSIGHT Insight Leakage management Leakage is a useful measure for the condition of water network assets and the effectiveness of the overall supply operation L eakage has been a useful focus for UK water utilities. The setting of leakage targets in the mid-1990s stimulated a wave of innovation in the industry that has resulted in levels falling by more than a third over the past 20 years. Now around the 20% mark, the UK's water industry leads much of the rest of the world in this regard. Politics and regulation have driven many of these leakage improvements to date, but there are important environmental THE CONCEPT • oNet is a suite of technologies to turn legacy infrastructure into smart water networks • It collects and analyses water pressure and automatically controls pressure • oNet has helped reduce leakage and energy use by 20% and cut burst frequency • It allows pressure to be set manually to manage supply NEED TO KNOW 1 Leakage is expected to fall to 2,750 megalitres a day by 2040 2 Pipe replacement programmes produce a short-term benefit 3 Excess pressure and network turbulence mean leakage levels remain higher than they could be 4 Excesses of pressure accelerate leakage THE VERDICT "Leakage continues to be an important problem to address and provides a great indication as to the health of the water network. Reducing it is just one of the benefits achieved from these wider reaching infrastructure improvement programmes" Keith Hilson, i2O and operational reasons – including population growth, urbanisation and more frequent extreme weather events – for reducing it further. Focusing on leakage in isolation, however, would be a big mistake. Leakage is not an arbitrary metric, but rather a symptom of the wider challenges facing providers. Much like their peers elsewhere in the world, UK water utilities are largely reliant on Victorian Age infrastructure and must constantly firefight a deluge of customer complaints and network failures to keep the taps on. Severity Excess pressure and network turbulence mean that leakage levels remain higher than they could be, bursts happen more frequently and the cost of maintenance and energy bills remain unnecessarily high. Without further improvements, leakage and other network incidents are likely to increase in volume and severity over the coming years. Leakage levels are a useful surrogate measure for the condition of water network assets as well as the effectiveness of the overall supply operation. They are, however, a blunt instrument. Looking at leakage in isolation can cause providers to focus only on fixing the leaks themselves rather than addressing the underlying causes of those leaks. While excesses of pressure accelerate leakage, the weight and sheer volume of water flowing through distribution networks is such that sudden pressure fluctuations have the potential to cause considerable damage to infrastructure, creating more bursts and aggravating existing leaks further. Sudden waves Shutting down areas of the network and rerouting water in order to patch up or replace the leaky pipework could be part of a wider solution, but in isolation pipe replacement programmes produce a short-term benefit at best, and all too o'en none at all. The underlying cause of the problem might sit elsewhere in the network, so plugging the leak simply shi's it elsewhere. Problems are never truly fixed and water utilities end up chasing their tails. Furthermore, any work on the network that involves isolating the mains can create transients, sudden waves of pressure that travel for long distances through the network at velocities approaching the speed of sound. The same effect is also created by other sudden changes, such as when large customers start and stop taking a lot of water from the network, or as water supply pumps are turned off and on. The energy of these significant pressure variations is dissipated through noise, heat and network damage. It can also stir up sediment and cause loose surfaces to be dislodged, discolouring the water supply and creating more complaints. The biggest danger, however, is the potential for pressure vacuums to form and suck in untreated water from outside the network, creating a significant risk to human health from waterborne bacteria and viruses.

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