The preservation of the architectural heritage is generally associated with the rehabilitation of the castles, thus ignoring all the art works and hydraulic structures. In this research, we are interested in the oldest masonry tank with a capacity of 1000 m3 in Fort National city, built by military engineers during the French occupation. This work is an architectural masterpiece, made since nearly 150 years, with natural stones extracted from the city’s quarry and disused since the mid nineties. Its cover slab was used as a tennis court during the French presence, but since the 1980s, this slab has been used as a parking area for vehicles. Since this substantial change in the use of the cover slab, this structure has been subjected to several external loadings. This architectural heritage already well integrated as urban infrastructure deserves to be rehabilitated in order to give it a new life and integrate it into the drinking water supply system of Fort National city in order to relieve the districts below the city. This research presents a methodology for assessing the performance level of this work. The study recommends preventing operating overloads exceeding the limited value of 2.00 tons/m2 in order to avoid exceeding the allowable stresses which could damage the resistant elements of the structure. This research fits into a practical environment of the engineering by combining analysis software with design codes and by the applicative character of the proposed approach. It is clearly part of a sustainable development approach in that the restoration of an architectural heritage makes it possible to provide a solution to a new challenge facing humanity and the planet, which is the rational management of drinking water resources in the face of climate change.