CHENNAI: The State government has given in-principle approval for Rs 3,108.55 crore Ring Main System (RMS) to connect city’s drinking water sources into a single network to improve reliability of supply across the city.
At present, the city’s water supply is drawn from surface water reservoirs, groundwater sources and desalination plants. Water is treated at 5 Water Treatment Plants (WTP) and 3 desalination plants and supplied through separate transmission systems.
When supply from one source is stopped, areas depending on that source face shortages even if water is available elsewhere, as there is no mechanism to divert water between systems. The proposed RMS seeks to address this by interlinking all 9 water sources, including the upcoming desalination plant, through a closed loop of pipelines covering the Greater Chennai Corporation area.
Under the plan, water from each source will be pumped to a 98 km-long ring main pipeline laid using mild steel. From this ring, water will be supplied to all 84 Water Distribution Stations (WDS) in the city, allowing supply to be adjusted based on availability.
The system comprises pumping stations, feeder mains, transmission mains and the ring main, forming a closed-loop network around the city. This configuration is intended to ensure proportionate distribution to all water distribution stations even during shutdown of individual sources.
The system will be operated through automated controls, through a centralised SCADA-based master control centre, with real-time tracking of pressure, flow and water quality across the network with sensors monitoring pressure, flow and water quality, and valves regulating supply across the network.
This was one of the announcements made by Finance Minister Thangam Thennarasu during the 2025–26 budget in the State Legislative Assembly.
The city currently supplies about 1,200 million litres per day (MLD) of water to a population of around 85.7 lakh.
The RMS has been designed to carry up to 1,762 MLD, based on projected drinking water demand up to 2057. The project is proposed to be implemented with loan assistance from the Asian Development Bank and is expected to be completed within four years.