Framework Directive (WFD) 60/2000/EC and finding ways of Water Distribution System’s (WDS’s) Full Water Cost (FWC) calculation, was the trigger for the preparation of this thesis. An increase in water price is expected to follow the full water costing, so the general objective of the thesis was the documented alleviating of consumers impact by implementing Non-Revenue Water (NRW) strategies. A series of methodologies and tools were developed in order to find the equilibrium level of efficient (in terms of water volume) and reciprocating (in terms of revenue) water uses or otherwise the sustainability level of urban water uses, while a) applying full water costing and b) implementing operating pressure management within the limits of Economic Annual Real losses (EARL). It is demonstrated through the proposed methodology that application of pressure management within the EARL limits can absorb large increases in the water price and lead simultaneously to sustainable levels the various system’s demands. The main tools required for completing this thesis (both for shaping the methodology and for the implementation in a real water network), was the FWC calculation method, the formulation of the residential water demand equation and the price elasticity of residential water demand, the method of calculating the economic level of leakage (ELL - Economic Level of Leakage), the pressure management techniques and the full hydraulic model of the Water Distribution System (WDS). The thesis is divided into the basic methodology and four distinct pillars. The first pillar is the analysis of the water balance terms and strategies to reduce real water losses and in particular the analysis of the operating pressure implementation due to network’s segmentation in hydraulically isolated areas, called District Metered Areas (DMAs) and Pressure Reducing Valves (PRVs) installation. The second pillar is the search for ways of calculating the FWC components (Direct Cost – DC, Environmental Cost – EC, Resource Cost – RC) defined by the WFD. The other two pillars are the calculation of the consumers’ response to water price change and the calculation of water price elasticity of residential demand and the proper hydraulic simulation of WDSs through the use of suitable software.The basic methodology analyzes how to approach the problem and the connection of the four pillars with the broader objective of finding the system's sustainability level by increasing the FWC and by implementing simultaneously pressure management in the limits of EARL. The concerns and the theoretical background of the methodology are initially analyzed. In particular, the reaction (due to elasticity of demand) and the system’s balance achievement by increasing the water price because of FWC implementation was investigated. Subsequently, before the detailed development of the remaining pillars of work, the methodologies that connect the various procedures are presented. EARL calculation mechanisms are developed due to pressure management application. The FWC, the elasticity of water demand, the terms of the water balance and finding of EARL levels were combined, so any increase in the actual FWC to cause implementation of pressure management in the EARL limits and finally all water balance components will balance to the sustainability levels. Major general concerns were finding the variation’s equations of the System Input Volume (SIV) components when the water price varies or when variation of the “water losses”, “illegal use” and “invoiced consumption” water volumes takes place. The application of the proposed methodologies was successfully implemented in Kozani WDS.The main conclusions were the beneficial effect of pressure management, when the water price increases, in all components of the water consumed, the operating pressure and the UARL (Unavoidable Annual Real Losses) and CARL (Current Annual Real Losses) indicators. The real losses water volume decreases rapidly when applying the “increasing water price with simultaneous pressure management (in the levels of EARL) implementation” scenario, while in the “increasing water price without NRW reduction measures” scenario the “real losses” water volume increases slightly. When applying pressure management measures at the level of EARL, there is less decrease of invoiced consumption. In the case of applying pressure management measures (in the EARL limits), the water price is not only increased at a slower rate, but for an initial increase of water price by 100%, the system balances at a reduced water price level compared to the initial. The average network’s pressure and the UARL indicator are increased with little pace water price increases without pressure management measures, while in the case of pressure management are reduced dramatically.
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