A Practical Approach for Prioritizing The Replacement of Water Pipes in Mexico City

Abstract

In Mexico City, one of the largest cities in the world, large losses occur in the drinking water distribution system, mainly due to the age of the pipes and the type of materials used in water delivery to the end user. In the past, most of the water distribution networks in the city were built with asbestos-cement pipes. Currently, policies dictate that they be replaced by polyethylene pipes. While the size of the city leads to limited financial resources, it is important to prioritize pipe replacement; therefore, a practical approach based on Deterioration Point Allocation (DPA) is proposed to define the priority level. In the next set of factors, each is represented by appropriate indicators:

1. 1. Failures in pipes and service connections

   a. Number of failures (leaks) in pipes repaired in one year for every 100 km of pipeline.

   b. Number of failures (leaks) repaired in one year per 1000 service connections.

   c. Spatial concentration of failures (leaks) in a pipe

   2. Annual pipe and service connections rehabilitation or replacement level per year.

   3. Operating parameters of the network: intermittent water supply, water pressure, and water losses

   4. Deterioration status of pipes and service connections

   5. Land subsidence

A score and a weight are assigned to each factor. The score depends on the values of the indicator, and the weight on the relative importance of the factor. The final score is used to prioritize the replacement and it is calculated by adding up the scores of each factor.

Considering that available information is incomplete and unstructured, two levels of use are proposed: basic (with available data, using MS Excel) and advanced (using a GIS).