Singapore’s HDB pilots UrbanWater Harvesting System in existing estates

The Housing and Development Board (HDB), a statutory board under the Ministry of National Development responsible for Singapore’s public housing, will be extending the UrbanWater Harvesting System (UWHS) to existing estates for the first time through a pilot project covering 89 blocks in two HDB towns.

HDB called for a tender for the installation of UWHS to harvest rainwater for non-potable uses at the common areas of 89 blocks across Yishun and Jurong. It is estimated that about 15 UWHSs will be installed, potentially reaping water savings of about 17,500m3 per year, or the average yearly consumption of potable water of over 85 units of 4-room HDB flats.

Schematic of how the UrbanWater Harvesting System works (Photo credit: HDB).

First introduced in all suitable Build-to-Order (BTO) projects in 2018, the UWHS is designed to maximise the volume of rainwater collected by harvesting stormwater surface runoff from the ground area surrounding multiple residential blocks. The stormwater from surface runoff that is discharged into an estate’s surrounding drainage system will first be channelled into the UWHS’ harvesting and detention tank.

The system’s rainwater harvesting capability and water detention capacity allows for a single UWHS to harvest from and dispense water to as many as 12 residential blocks, for non-potable uses. Some of these uses include the washing of common areas and watering of plants in HDB estates, where the UWHS can save up to 50% of water usage for these purposes. In addition, the channelling of stormwater into the UWHS’ harvesting and detention tank can mitigate potential flood risks in an estate in the event of a heavy downpour by slowing down the rate of discharge of stormwater into the drainage system downstream.

Unlike in new BTO projects where the UWHS infrastructure can be planned and designed upfront to ensure it is located where the most amount of rainwater can be collected through the drain networks, retrofitting the UWHS into existing estates is more challenging as it involves analysing the flow of the rainwater in the catchment area and identifying suitable locations to accommodate the system amidst other essential services infrastructure that would already be in place underground.

Tan Meng Dui, CEO of HDB, commented: “With the vast majority of our residents staying in existing HDB estates, we have taken a further step to pilot the system in existing HDB estates. While such brownfield developments will be more challenging to implement, compared to building the system as part of a new HDB development, the extension of the UWHS to existing estates will help to level up the sustainability provisions of our existing estates, and bring the benefits of green and sustainable living to more residents and towns.”