PUB maintains the sewerage reticulation system in Singapore with about 3,600km of public sewers and around 100,000 sewer manholes. PUB conducts systematic checks and carries out repairs on defective sewers to enhance the structural integrity of the sewerage system and to prevent the pollution to waterways.  

PUB adopts a preventative approach of enhancing the reliability of sewerage system by restoring the life-span of the sewers through on-going rehabilitation program. The older sewers would be surveyed and inspected, followed by rehabilitation works where required. Rehabilitation of the sewers would result in these benefits:

• Restore structural integrity of the sewerage system
  This rectifies the defects that could lead to chokes, leaks and structural failure of the pipes.
• Prevent overloading of the sewerage network 
  This prevents overloading of pipes and WRPs that could affect NEWater production with the reduction of groundwater and seawater that infiltrate into sewers.
• Restore flow efficiency
  This enhances conveyance capacity of the sewer with a smooth lining installed.
• Prevent pollution to waterways
  This minimises pollution to waterways and reservoirs with the leaky sewers rectified.

Rehabilitation Programme
Phase 1-3 (1996-2014): Public sewers mainly in urban areas, Marina Reservoir Catchment, other Water Catchments and along southern coastal areas were rehabilitated.

Phase 4 (2009-2019): Public sewers within Punggol & Serangoon Reservoir Catchments and other parts of Singapore were surveyed and inspected, followed by rehabilitation works where required.

Phase 5 (2017-2024): Public sewers for whole of Singapore. Ageing sewers, which are more than 40 years old, will be rehabilitated, while sewers that are between 20 and 40 years old will be inspected and rehabilitated based on the assessment of their conditions.