water usage information

Toilets
Toilets usually account for a significant portion of total water demand in an office building. Based on typical usage patterns, 6/3 L dual flush toilets have an average water demand of 4 L/flush. With higher drainage grades, flush toilets can operate at 5/2 L or lower, reducing average demand per flush to less than 3 L/flush. There are different types of water efficient toilets on the market and in production, ranging from low and ultra low flush toilets to composting toilets that use no water at all.

Taps
Adjusting the flow rate of taps while maintaining spray pattern through the installation of flow regulating tap aerators can significantly reduce tap water use in hand basins and kitchen sinks. Typical flow rates for non-efficient taps are usually 10-12 L/minute, which can be reduced to 2.5 L/minute with the installation of appropriate flow regulators. Infrared Innovations in Water: Ozwater Convention & Exhibition, Perth, 6-10 April 2003 tap controllers reduce the duration of the flow of water, by only operating when the sensor is activated. These taps require energy to operate, and are more expensive. A combination of flow regulated and infrared taps can achieve significant savings in water demand.


Showerheads
While showering may be the largest source of residential water demand, shower demand is not as high in commercial buildings. Typical non-efficient showerheads have a flow rate of approximately 11 L/minute in use. AAA-rated showerheads have flow rates between 7 and 9 L/minute and highly efficient showerheads can have flow rates of 5 L/minute or less. Showers can also be fitted with digital readout meters that show the user the amount of water being consumed and the duration of the shower. This can encourage the user in an office building situation to reduce water demand for showers.

Roof gardens
Roof gardens or green roofs in commercial buildings can play a part not only in water and wastewater management but also in improving the energy performance of the building. There are two types of green roofs – extensive and intensive. Extensive green roofs have a thin growing medium, have lower plant diversity and are relatively inexpensive. Intensive green roofs have a deeper soil substrate, have a greater diversity of plants and habitats, potentially have greater energy efficiency and stormwater retention capabilities and a longer membrane life. Roof gardens can reduce the ‘urban heat island effect’, the overheating of urban areas due to an increase in paved and concreted areas in relation to ‘green’ areas. This reduction may lead to substantial energy savings. Other important benefits include prolonging roof life, filtering of airborne particles, sound insulation, creation of aesthetically pleasing landscapes and stormwater retention (Peck & Kuhn, 2001). Life cycle costing calculations undertaken by the National University of Singapore on rooftop gardens have found that extensive green roofs cost no more than conventional roofs when the energy savings are considered (NUS, 2002). In a commercial building, roof gardens can be used either for stormwater retention or to evapotranspirate the effluent generated from wastewater treatment plants. In the latter case it is important to ensure that the roof gardens are protected from rain, in order to maximise their evaporation capacity. The type of plants to be used and the location of the roof garden need to be carefully chosen to maximize evapotranspiration of effluent.

(taken from notes "Sustainable water management in commercial office buildings" Sydney University of Technology