Water end-uses in Brazilian office buildings

Lúcio Costa Proença e Enedir Ghisi
Resources, Conservation and Recycling

The objective of this study is to estimate the main water end-uses in ten office buildings located in Florianópolis, southern Brazil. Analyses on the influence of the size of the sample interviewed to estimate the water end-uses and on the need of applying a sensitivity analysis to eliminate the difference between the estimated and the measured water consumption were also performed. The estimates were performed by interviewing the occupants of the buildings and by measuring water flow rates. From the interviews, the daily amount of time and frequency of use of water for toilet flushing, taps, cleaning and other uses were obtained. As for the water flow rates, they were measured for taps and bowl-and-tank toilets. For toilets with wall flushing valves, the water flow rate was obtained from a Brazilian Standard which suggests 1.7 l/s. From these data, the monthly water consumption in the buildings and the water end-uses were calculated. The estimated water consumption in each building was compared with the measured consumptions supplied by the local water utility (considering the average consumption from September 2004 to August 2006). It was verified that toilet flushing is responsible for 52–84% of the total water consumption in the ten buildings, followed by water use from taps in seven buildings. It was also found that the sensitivity analysis is unnecessary and that the estimation of water end-uses based on interviews of small samples of the occupants of the buildings (more than 40% of the occupants) can lead to acceptable results. The main conclusion that can be derived from this work is that programmes for water conservation in office buildings should first focus on toilet flushing as this responds for a high percentage of water consumption in such buildings.