March 20, 2014
Safe, clean, palatable water costs money. Leaks incur additional costs as even more water must be found and treated. Dealing with leakage is a universal challenge for cities but none have responded more effectively than Tokyo.
Starting in the 1980s the Tokyo Metropolitan Government Waterworks Bureau turned to nickel-containing stainless steel pipe Type 316 (UNS S31600) for the distribution systems that take water from the sub-mains to final destinations in homes, offices and industrial plants. It was a gradual process that took 24 years to complete, but now after two decades of service it is possible to calculate the benefits.
Leakage and its costs
Lead was the preferred material for water connections because it is soft and malleable and easy to work with, especially for the last few meters from sub-mains to offices and residences. Once lead pipe is in the ground, however, various forces can act on it.
Combinations of human activity – heavy traffic and vibration or construction work – and natural forces such as unequal ground subsidence and earthquakes can cause the soft lead pipes to deform, become detached or even break.
The result was that in the early 1960s over 20% of all of the water suitable for human consumption in the Tokyo distribution system was lost to leakage. Water shortages were chronic and rationing was occasionally required for about one million Tokyo households.
Historically approximately 3% of the leakage repairs of the Waterworks Bureau was on water mains, with 97% on the distribution lines of 50mm or less that take the water from the public system to internal systems in buildings.
Health and financial benefits
In switching to stainless steel pipes the Tokyo Government has made a significant investment in the health of its citizens. The reliability of the water supply has increased and the leakage rate has been reduced from 20% to 2% (2012) and is perhaps the lowest of any metropolitan area in the world.
Supplying and distributing water in Tokyo will always be a challenge because of the limited water resource base. The dramatic reduction in leakage from the system allows the most efficient management and use of a scarce resource as the per capita amount of water that has to come from reservoirs and pass through treatment plants has been reduced. And while not a formal objective of the campaign against leakage, there is the additional benefit of reducing the potential exposure to lead.
This achievement of long-term planning and implementation has led to many engineering and institutional award.