Planning a green building? Don’t miss these 5 sewage design essentials

When we think of green buildings, we often picture solar panels on rooftops, breezy corridors with natural light, and energy-efficient design. However, there is also one essential system that runs quietly beneath the surface – often left out of the conversation, yet critical to sustainability – the underground drainage and sewage treatment system. Yes, it may not be glamorous, but it is absolutely critical and one of the most important aspects to get right when planning a green building. An overlooked or poorly planned wastewater design can lead to serious structural issues, hygiene concerns leading to spread of water-borne diseases, and even cost you that coveted green certification. On the flip side, a smart sewage system can boost your building’s IGBC score, enhance safety, and support long-term sustainability goals. So before you break ground or file that blueprint, make sure this invisible backbone is built to last. Here are 5 sewage design essentials that every green building must include.

Efficient systems – Underground drainage to Treatment

When planning a green sewage waste water system, it is essential to consider water as a circular resource. This journey begins with waste water collection, followed by underground conveyance, sanitation and treatment, and finally, water reuse. Every stage needs the right infrastructure to function seamlessly.

Discharge: The first step is discharge, and one can start with a durable internal drainage system, that can handle soil, waste, and rainwater (SWR) and prevent water logging. The system should ensure structural safety, durability and efficient conveyance of wastewater from kitchens, bathrooms, toilets and utility areas (sewage).

Conveyance: In green building, conveyance – which typically refers to the transport of sewage from the point of generation (toilets, sinks, showers etc.) to the treatment system. It should also have integrated Non-Return valves (NRVs) that prevent backflow – a must for low-lying or flood-prone zones.

Sanitation & Treatment: This is the first stage of sewage treatment, and in green buildings, pre-fabricated septic tanks or bio-tanks are commonly used. These tanks are crucial for primary treatment and Biological oxygen demand (BOD) reduction — reducing biological load by up to 50-60%, as per a report by NITI Aayog. This staged approach improves STP efficiency and reduces energy costs. For IGBC compliance and reuse, a proper STP using a multi-stage process for cleaning wastewater [MBBR (Moving Bed Biofilm Reactor)/ SBR (Sequencing Batch Reactor)/MBR (Membrane Bioreactor) + tertiary treatment] is required as per CPCB/state norms.

Choose Durable, High-Quality Materials that are cost effective

A green building should be maintenance-friendly, not maintenance-heavy, while ensuring optimal hygiene. The choice of materials for SWR and underground drainage pipes is critical to achieving this. Additionally they should also minimise the long-term maintenance cost to the owner — making the system maintenance-free and highly cost-effective.

Select SWR pipes manufactured from high-grade PVC that are maintenance-free, resistant to rust, corrosion, and deposit build-up. Smooth internal surfaces should further prevent scaling, minimise friction losses, and maintain high flow rates.

For outdoor plumbing systems, such as swimming installations, one must prioritise pipes with advanced UV-resistance features, as these remain intact even under prolonged exposure to sunlight.

For underground drainage, opt for pipes that are eco-friendly and made with advanced foam-core technology—a durable, and cost-effective solution that reduces maintenance and replacement frequency while providing a stronger foundation for sustainable drainage. These pipes should withstand extreme temperature fluctuations, exhibit excellent chemical resistance, and be fully corrosion-proof. Also ensure all underground pipes are lightweight and easy to handle, facilitating faster, safer installation without compromising long-term performance.

Prevent Leakages, Rodent Damage

Leaks, pest intrusion, and pipe degradation can compromise both structural safety and hygiene. For a truly sustainable building, rodent-proof materials are essential. Choose pipes from trusted manufacturers that are strong, durable, and engineered with anti-rodent properties to minimise maintenance needs, prevent leakage risks, and safeguard the building’s long-term structural integrity. This also helps prevent water logging and ensures seamless flow throughout the drainage system.

Reuse Treated Water – And Color Code It

In a truly sustainable system, sewage water is not wasted — it’s repurposed. Treated wastewater can safely be reused for non-potable purposes like toilet flushing, landscaping, gardening, car washing, etc. This reduces dependence on freshwater and makes your project more water-resilient. But to make this work, two things are essential — proper reuse planning and pipe color coding.

Colour-coded pipes allow for quick visual identification of potable and non-potable lines, preventing hazardous cross-connections. Each pipe type—SWR, underground drainage (UGD), and reclaim—should have a distinct colour. This practice enhances safety, streamlines maintenance, and can contribute to earning valuable green building points under the Water Efficiency category. IGBC points are awarded for actual treatment and reuse of water (via dual plumbing, sub-metering), not for pipe color itself.

A separate stormwater network with rainwater harvesting is as vital as underground sewage

Sewage planning doesn’t stop at toilets and kitchens. Balconies, terraces, and parking lots must be accounted for too. During monsoons, if rainwater isn’t routed properly, it can mix with sewage, overburden STPs, or cause backflow — especially in high-density buildings. This is where a dedicated surface drainage system becomes vital. Plan for modular HDPE drains designed for driveways, terraces, and balconies. These are load-bearing, easy to clean, and built to handle high rainfall intensity. The National Building Code and IGBC Net Zero Water guidelines mandate that rainwater be routed separately from sewage to prevent contamination and allow rainwater harvesting. By separating rainwater from grey and black water lines, buildings can protect their sewage systems from overflow while also enabling rainwater harvesting. IGBC gives credits for rainwater harvesting & stormwater management.

Choose systems that are high-quality, cost-effective, and modular. Independent households need not install oversized systems designed for high-rises; instead, they can opt for modular solutions available from reputable, established brands in the market. Sewage design isn’t just about discharge — it’s about responsibility. A well-designed sewage system is the backbone of a responsible, sustainable building. When built right, with high quality durable solutions from trusted manufacturers, it reduces risk, saves resources, and promotes sustainable buildings and living.