The objective of this paper is to compare the various methods of rainwater tank sizing suggested in the Brazilian standard NBR 15527 with the Neptune computer programme. The rainwater tank capacities were estimated for homes in three cities in Brazil: Santos, Palhoça and Santana do Ipanema, chosen due to their different rainfall patterns. Different roof areas, potable water demands, and rainwater demands were analysed using each method. The same cases were simulated in Neptune, which provides the potential potable water savings for each tank capacity. The tank capacities obtained by the other methods were also simulated in Neptune in order to obtain their respective potentials for potable water savings. Thus, it was possible to compare the rainwater tank capacities, the potential for potable water savings obtained with each method, and the applicability of each method for different rainfall patterns. The results showed that some methods are not suitable for certain rainfall patterns, since they always provide the same tank capacity, regardless of rainwater demand or rainfall; and this may result in under- or oversized tanks. By contrast, using Neptune, it was possible to size the tanks for all the simulated cases; and it was the only method whose tank sizing provided more reliable results when compared to other NBR 15527 methods, due to the rainwater demand in all cases and rainfall patterns.
Rainwater harvesting; Rainwater tank sizing; Sizing methods
