The production of NEWater, Singapore's ultra-clean reclaimed water, is an engineering miracle that begins with another: the Deep Tunnel Sewerage System (DTSS). This massive, $10 billion underground project is not just a sewer; it’s the backbone of Singapore's water security, functioning as a colossal, gravity-powered used water "superhighway."

Designed to last 100 years, the DTSS ensures that virtually every drop of used water on the island is collected, treated, and made available for high-grade purification into NEWater.

💧 How the DTSS Feeds the NEWater Plants

The DTSS fundamentally changes Singapore's used water management from a distributed, energy-intensive model to a centralized, gravity-fed one.

• 1. Link Sewers: A network of smaller link sewers collects used water from the existing, shallower sewerage pipelines beneath the city.

• 2. The Gravity Flow: This collected used water is channeled into the Deep Tunnels, which run up to 55 meters below ground. Because the tunnels are built on a downward slope, the water is conveyed entirely by gravity. This eliminates the need for dozens of intermediate pumping stations across the island, which were a hallmark of the old system.

• 3. Centralized Treatment: The tunnels bring all the used water to a few centralized, state-of-the-art Water Reclamation Plants (WRPs) located along the coast:

  • Changi WRP (The terminus of DTSS Phase 1, completed 2008).

  • Tuas WRP (The terminus of DTSS Phase 2, scheduled for completion in phases from 2027).

• 4. NEWater Factory Integration: Crucially, the NEWater factories are often built integrated with or atop these centralized WRPs (e.g., the Changi NEWater Factory is on the roof of the Changi WRP). Once the used water is treated to international standards at the WRP, it is immediately channeled next door or upstairs for the final three-stage purification process into NEWater.

This centralized, gravity-fed system is highly efficient, reliable, and secure—essential qualities for the core water source of a nation.

🗺️ A Project of Immense Scale and Benefit

The DTSS is one of the most ambitious engineering projects in Singapore’s history, implemented in two phases:

✅ Key Benefits Beyond Clean Water

The DTSS is a masterstroke in long-term planning, delivering major non-water benefits for land-scarce Singapore:

• Land Optimization: The DTSS allows for the phasing out of several older, decentralized water reclamation plants and over 100 intermediate pumping stations. This frees up approximately 150 hectares of land—nearly twice the size of the Singapore Botanic Gardens—for higher-value development, like housing and commercial space.

• Enhanced Reliability: The use of gravity minimizes mechanical failure points and energy use compared to the old, pump-heavy system, making the network far more robust and cost-effective to run over its projected 100-year lifespan.

• Pollution Prevention: By routing all used water deep underground, the system eliminates the risk of accidental discharge or pollution into the surface-level rainwater catchments (Tap 1), thereby enhancing the quality of all water sources.

In essence, the DTSS is the silent, colossal enabler that ensures Singapore can close its water loop and sustain its growth for generations to come.

Would you like to know more about the integration of the Tuas Water Reclamation Plant with the Integrated Waste Management Facility (IWMF) in Phase 2, a concept known as the Tuas Nexus?