Singapore's 4 National Taps refer to the 4 sources of water supply, i.e. (1) Local Catchment, (2) Imported Water, (3) NEWater, and (4) Desalinated Water.
• The 1st 'tap' Local Catchment, refers to the supply from our local water catchments and reservoirs.
• The 2nd 'tap' Imported Water, refers to the import of water from Malaysia under the 1962 Water Agreement. Under the 1962 Water Agreement, Singapore can draw up to 250 million gallons of water a day from the Johor River, and Singapore is obliged to provide Johor with treated water up to 2% of the water we import. The 1962 Water Agreement will expire in 2061. Constructed by PUB under a 1990 agreement with Johor supplementary to the 1962 Water Agreement, the Linggiu Reservoir is located upstream of the Johor River Waterworks and releases water into the Johor River to supplement its flow. This enables abstraction of raw water at the Johor River Waterworks which is owned and operated by PUB for treatment.
• Our 3rd 'tap' NEWater, is ultra-clean, high-grade reclaimed water produced from treated used water that is further purified using advanced membrane technologies and ultra-violet disinfection.
• Our 4th 'tap' is seawater desalination where freshwater is obtained by removing salt from seawater through the reverse osmosis process. Desalination is the process of turning seawater into drinking water. Singapore currently uses reverse osmosis for its desalination. This process produces pure drinking water by passing seawater through membranes to remove dissolved salts and minerals. Producing desalinated water is energy intensive. Moving ahead, PUB is exploring technology to bring down the energy needed for desalination, such as electro-deionisation and biomimicry. Electro-deionisation is a method that uses an electric field to pull dissolved salts from water. Biomimicry is the mimicking of biological processes by which mangrove plants and euryhaline fish extract freshwater from seawater using small amounts of energy.
Diversification of our sources of water through the 4 National Taps ensures a reliable and resilient water supply. For more information, you may visit the PUB's website here.