Singapore's Four National Taps refer to the 4 sources of water supply, i.e. (1) Local Catchment, (2) Imported Water (from Johor), (3) NEWater and (4) Desalinated Water.

The first 'tap' refers to the supply from our local water catchments and reservoirs. The second 'tap' refers to the import of water from Malaysia under two water agreements. Our third 'tap' NEWater, leverages on a 3-stage process of ultra-filtration/ micro filtration, reverse osmosis and ultra violet radiation to reclaim water from our used water effluent. Our fourth 'tap' is seawater desalination through which freshwater is obtained by desalting seawater through the reverse osmosis process. The Four National Taps help to diversify our sources of water to ensure a reliable and resilient water supply.

Currently, about half of Singapore's total land area is used as water catchments. This will increase to two-thirds of the island when the new Marina Reservoir and the first phase of the Seletar-Serangoon Reservoir Schemes are completed.

Singapore's current per capita domestic water consumption is about 158 litres per day. Notwithstanding, PUB has rolled out a series of demand management initiatives, such as the Water Efficient Homes programme and the 10-litre challenge initiatives, to further reduce per capita water consumption to the targeted level of 155 litres per day by 2012.

Under the Singapore Green Plan (our blueprint towards environmental sustainability), the target for the supply of water is to have at least 25% of our water supply derived from unconventional sources by 2012. This is achieved by increasing the supply of water through NEWater and seawater desalination.

Since the introduction of NEWater in 2003, its demand has increased rapidly. In addition to the 4 NEWater factories which have capacities to supply 15% of Singapore's total water demand, a fifth NEWater factory at Changi will be constructed. When completed in 2010, NEWater can meet up to 30% of Singapore's total water demand.