Decentralized decision making and lack of regulation lead to the existence of significant differences in the price of water for residential uses among Spanish cities. Why do these differences persist? Do they have to do with cost differentials or do they result from political and business interests? Can users perceive water tariffs as fair or is there unfairness among citizens when it comes to the access to water? We find that some of the differences are due to arbitrary decisions made by policy and business decision makers, so it is recommended that a regulation be adopted that sets criteria for guidance in tariff design, especially for lower levels of consumption within which water is considered a merit good.