Sensitivity of water distribution costs to design and service standards : a Philippine case study

This technical note describes a study undertaken for the Local Water Utilities Administration (LWUA) and the Rural Waterworks Development Corporation (RWDC) to evaluate the impact changes in design and service standards on the costs of water supply projects in selected small towns and rural areas of the Philippines. Linear regression analysis was used to evaluate the magnitude of cost reduction to various modifications in design standards. In small urban schemes the greatest cost savings could be achieved by (a) reducing minimum pipe diameters from 100 to 38 or 50mm, (b) limiting the per capita use to 140 liters/day, (c) providing a mix of house connections and public standposts, and (d) neglecting the fire demand provisions. Changes in available head in the distribution system had relatively little effect on cost reduction. In rural areas where only public standposts were installed, substantial cost savings ensued from (a) using PVC pipes instead of galvanized iron and (b) limiting the per capita use to 40 liters/day. The increase of the number of households per standpost resulted in an increase, rather than a decrease, in distribution costs.