Water Supply System Performance for Different Pipe Materials Part II: Sensitivity Analysis to Pressure Variation

In water supply systems there are many situations during normal operation that induce the occurrence of pressure transients, where high pressures are followed by low, sometimes even negative pressures. These transients may cause ruptures in pipes creating thus leaks or opportunities for contaminants to enter the water supply system. Thus severe pressures transients should be avoided or adequately controlled in potable drinking systems. The level of service provided by water distribution systems is an important matter in the water industry of today. However, the measure of the performance of a pipe system network is not a straightforward task. In this study the performance of pressures in two networks (a cast iron network and a polyethylene network) with the same typology was compared. The transient state conditions were induced by different typical hydromechanical devices operation characterised by a sudden pumps trip-off, a leakage occurrence and a closure of an automatic control valve. For the hydraulic simulations, advanced models based on numerical computation for steady and transient state conditions were used. A performance evaluation model was developed to analyse each type of situation since the simulation time period and the concerns regarding the system behaviour can be fairly different.