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sewers. This is certainly the case in Orangi and preliminary evidence suggests that the situation will be similar in Faisalabad. Involvement of residents shifts the interface between the 'private and public' domains from the plot boundary to the point at which local sewers discharge to collector sewers and allows a more integrated approach to be taken to local sanitation and drainage improvements. This more integrated approach should arguably allow schemes to tackle the problem of sand entering sewers through house connections by encouraging residents to provide grit traps on sullage lines. It should also be possible to encourage them to provide traps on connections to deter cockroaches and rats. However, more field research is required to determine the best connection arrangements and to develop methods to encourage residents to adopt them. |
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4.3
Construction Details and Procedures |
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4.3.1
Pipe Materials and Jointing |
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Government agencies in Pakistan specify spun spigot-and-socket concrete pipes with each spigot provided with a groove designed to allow the fitting of a rubber ring. While this should make the pipes flexible, the reality is that little faith is placed in the efficacy of the rubber rings and the normal practice is to finish each joint by filling the annulus between the spigot and the socket with cement mortar. This means, of course, that the joint is rigid rather than flexible. Early in the North-east Lahore project a decision was made to discontinue the use of rubber rings as they served no useful purpose once the decision to mortar the joint had been made. The pipes used in North-east Lahore were produced in one of the larger casting yards which had been approved by government. Pipes of 300 mm diameter and above were produced broadly in line with the requirements of the relevant ASTM specification, while 230 mm diameter pipes complied with BS5911. |
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In the informal sector, most sewers are constructed using plainended concrete pipes which are purchased from small local casting yards which also produce a variety of materials used in house construction and for other purposes. The pipes are |
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