Private water storage tanks are often considered as very inefficient devices than can only be justified in systems that suffer frequent water service interruptions. This paper presents the results obtained after studying four different aspects of this question: the effect of this kind of tanks on water losses, unaccounted for water, time modulation curve and energy losses (other implications, such as those related to water quality deterioration, remain out of the scope of the study). Conclusions for each particular point will turn uneven, specially highlighting the effect on the meter global error and unregistered water. In any case, all four points, as well as several additional issues to be considered, are described and evaluated.

Frontier efficiency methods have been recurrently used in the water sector to assess the performance of water utilities. These methods are also used for yardstick regulation, with greater efficiency being sought by creating competition between the utilities, which can have an impact on decision-making processes, such as tariff setting. This study analyzes the adequacy and limitations of these methods for regulatory purposes, particularly how they deal with data uncertainty and their capacity to manage large number of variables. In order to achieve this, two representative methods—a nonparametric technique (data envelopment analysis) and an econometric one (stochastic frontier analysis)—are applied to an audited sample of 194 water utilities. Results will show that the results from the methods may not be considered conclusive in the water sector and their application should be carried out with considerable reservations.

In this paper, an algebraic expression is presented to determine the optimum hydraulic gradient (J₀) in a pressurized water system. J₀ represents the economic level of friction losses (ELF), which is dependent on the network’s behavior as well as other parameters, including energy and the pipe costs. As these have prices changed over time, so has the value of J₀. The network-related parameter was obtained from the total costs function and the sum of the operational and capital expenditures. Because these costs exhibited an opposite trend from J, a minimum total cost exists, specifically, J₀. The algebraic expression, which was derived from the mathematical model of the network, was first calculated for the network’s steady state flow and was later generalized for application to a dynamic one. For a network operating in a given context, J₀ was fairly stable in terms of dynamic flow variations, providing valuable information. The first piece of information was the ELF itself, which indicated the energy efficiency of the system from the perspective of friction loss. The second indicated which pipes required renewal from a similar perspective. Thirdly, it provided a simple criterion to calculate the diameter of new pipes. Finally, as J₀ can be easily updated, when predictions are performed at the network’s designed time fail (e.g., growing urban trends, demand evolution, etc.), decisions can also be updated.

Hotels are a fundamental component within the tourist Spanish sector, and their role in water management turns out even more relevant taking into account the fact that tourist areas, in which they are generally located, are water scarce. Trying to go further from the standard ratios and estimations to plan water conservation, this work intends to really measure and quantify water use in rooms. Only by doing this, can subsequent conservation actions, now able to be reliably specified for each specific use, achieve a real success.