The Junior Changemakers’ Club | ‘India, Rethink Water’: Here Is How I Invented a Low-Cost Greywater Reuse System To Save Millions of Litres

This Children’s Day, we at The Better India reached out to young achievers across different sectors to learn about the change they wish to see in the country. From tackling a city’s water crisis to becoming a wildlife photographer at just 10, these kids have fresh ideas, high ambitions, and an inspiring spirit to make our nation truly a 'Better India'. 

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Dear India,

My name is Mannat. I am 18 years old, and I live in New Delhi. When I was growing up, a canal breach that supplied water to Delhi left my neighbourhood without water for days. People had to struggle for whatever little water was available.

Seeing this desperation made me realise how serious our environmental challenges are. It also pushed me to ask an important question: What systemic innovations can I design to strengthen environmental resilience in India?

One solution is recycling greywater — the wastewater from showers, sinks, washing machines, and courtyards — for non-drinking purposes. Reusing greywater reduces the pressure on clean drinking water sources and also reduces the amount of sewage produced.

When water use and sewage generation go down, the energy used for centralised sewage treatment and for transporting water also reduces. For example, according to a report by CLASP (2021), around 0.98 kWh of energy is used for every cubic metre of water in desalination, treatment, pumping, and wastewater processing in India. Similarly, a report by Griffiths-Sattenspiel & Wilson (2009) found that moving, treating, and using water in the US produced 290 million metric tonnes of CO₂ every year — about 5% of the country’s total carbon emissions.

Because India faces severe water scarcity and because centralised wastewater treatment contributes to rising carbon emissions, we urgently need solutions that allow households to collect, separate, recycle, and reuse wastewater on their own.

My applied research project addresses this need. It focuses on overcoming the challenges that households face when trying to adopt greywater reuse systems. I designed a solution called the Bilge Vessel and Scupper Valve, created to remove these barriers while ensuring efficiency and easy installation.

The system has two parts:

1. Scupper Valve (SV): This is a compact device that replaces the existing floor drain trap. It pumps greywater from all household sources — such as low-level shower outlets, kitchen sinks, washing machines, and even rainwater from the courtyard — directly to the Bilge Vessel. Importantly, it does this without any digging, sump creation, elevated platforms, or major retrofitting.

2. Bilge Vessel (BV): This is a three-bucket filtering system stacked vertically, inspired by Khamba Composting. It uses natural materials and physical baffles to filter the greywater it receives and stores the treated water for non-drinking uses such as flushing, mopping, irrigation, and car washing.

To improve the filtration efficiency and make maintenance simple, the filter media was placed in separate containers, stacked one above the other. They are interconnected to allow water to flow from the top to the bottom. Physical baffles were added to slow the water flow, increase retention time, ensure better contact with the filtration media, distribute water evenly, and help sediments settle.

This project has the potential to save both water and energy — not only within households, but across the entire water supply chain, including desalination, water transportation, leakage prevention, and sewage management.

Through this work, I have learned that human-centred design is built on empathy and flexibility. Problem-solving is a continuous process — ideas can always be refined, scaled up, and adapted to new contexts.

A spark of imagination, supported by creativity and thorough research, can lead to solutions with long-lasting impact.

My purpose is clear: to protect the environment that has shaped me, so that one day, in body and spirit, I can return to it.