Issues on service quality are crucial for water utility management and regulation. Omitting these aspects can lead to possible bias in estimating the efficiency of services. We integrate in a Translog cost function variables proxying this multidimensionality. Empirical results show that taking into account the level of quality of the delivered services has a significant impact on the measure of the efficiency computed from a stochastic frontier. Moreover we highlight that efficiency depends on ownership (public vs. private) and level of quality.