It is a generally recognised fact that the vast majority of leaks and leakage occur on service pipes to consumers properties. A similar pattern has been found during recent studies in Hong Kong. The high incidence of service pipe leakage has prompted some utilities and countries to supplement active leakage control policies with a comprehensive annual mains replacement or rehabilitation programme, with service connections being replaced at the same time as the distribution main to which they are connected. The banning of inappropriate pipe materials, for example unlined galvanized iron mains, and the adoption of newer materials such as polyethylene, which have superior hydraulic and corrosion resistance properties, has made a further contribution towards reducing leakage. In Tokyo, overall annual mains replacement rates of 1.1 per cent have been achieved consistently, with the emphasis placed on cast iron and asbestos cement mains which are being replaced at a rate of two per cent annually.
Stainless steel is the preferred material for service connections.
The average age of the pipe networks in Japan and Singapore is therefore relatively young. Minimal leakage control effort is expended in systems where high renewal rates are achieved. There is very little published evidence to support the economic justification for such high annual renewal rates which, although leading to low leakage levels, are reflected in considerably higher water charges. The philosophy appears to be that the achievement of low levels of leakage is alone sufficient justification. High replacement rates can only be entertained in relatively affluent parts of the world.