Chennai has long been wrestling with its water challenges, unpredictable monsoons, groundwater levels falling rapidly, and flooding during heavy rains. The Chennai Metro Water Supply & Sewerage Board (CMWSSB) recognized this early on and, since 2003, has required every building in the city to have a rainwater harvesting system. For Resident Welfare Associations (RWAs), understanding and implementing these guidelines is essential, not just to follow the law but to make a real difference in how the city manages its water resources.
Rainwater harvesting isn’t just about ticking a box. It’s about capturing nature’s gift and putting it to good use. When done right, it helps recharge groundwater, reduces the strain on municipal supplies, and even minimizes the flooding that Chennai’s streets often suffer from during heavy downpours.
Why rainwater harvesting matters in Chennai
The 2019 water crisis was a wake-up call for many. It exposed how precarious Chennai’s water situation really was, with many parts of the city facing severe shortages. The reliance on groundwater extraction, combined with insufficient rainwater capture, left the city vulnerable. This is why rainwater harvesting is more than a rule, it’s a lifeline.
By collecting rainwater where it falls, and either storing it for use or allowing it to seep back into the ground, RWAs can play a huge role in stabilizing Chennai’s water table. This, in turn, benefits every resident and business by ensuring a more reliable water supply throughout the year.
CMWSSB’s rainwater harvesting rules for RWAs
Since the enactment of the 2003 Municipal Order by CMWSSB, rainwater harvesting systems have been compulsory for all buildings in Chennai. Here are the key rules RWAs must follow:
Mandatory installation: Every building must have a functional RWH system to collect and store or recharge rainwater. Both new constructions and existing buildings are covered.
System types:
- Rooftop collection & storage: Rainwater is collected from rooftops via gutters and directed into storage tanks for non-potable uses such as gardening and flushing.
- Groundwater recharge: Surface runoff and rooftop rainwater are directed into recharge pits, soak pits, or borewells to replenish groundwater.
Maintenance requirements: Regular cleaning and upkeep of RWH systems are mandatory. This includes quarterly cleaning of filters and gutters and annual desilting of recharge structures.
Approvals & documentation: RWAs must submit proof of operational RWH systems to CMWSSB during inspections or when applying for water connection or renewal.
Compliance deadlines: Systems must be installed and fully functional before the onset of the monsoon season each year.
How to set up rainwater harvesting in your society
1. Survey your property
Begin by assessing your society’s layout:
- Identify all rooftops, drains, open land, and existing recharge points.
- A map showing where gutters and pipes will lead rainwater either to storage tanks or recharge pits.
2. Choose the right system type
Your society can opt for one or a combination of these systems:
- Rooftop rainwater harvesting (storage): Suitable for societies lacking open land but having ample rooftop area. Water is collected, filtered, and stored for later use.
- Recharge pits & borewells: Ideal for societies with open spaces, these allow water to percolate directly into the groundwater table.
- Surface runoff management: Percolation trenches or soakaways can be installed along pavements to capture and recharge runoff.
- Hybrid systems: Large societies often combine storage tanks with recharge pits for maximum effectiveness.
3. Installation before monsoon
Timely installation is crucial. Systems should be operational before June-July, the start of the monsoon, to capture maximum rainfall and comply with municipal orders.
4. Maintenance & monitoring
- Clean gutters and filters quarterly to prevent clogging.
- Desilt recharge pits and soak wells annually to maintain infiltration capacity.
- Flush storage tanks regularly to avoid stagnation and mosquito breeding.
- Maintain records of all maintenance activities and water recharge volumes.
5. Documentation & compliance
Keep all installation, maintenance, and inspection documents ready. Submit proof of functional RWH systems to the CMWSSB during water supply audits or property inspections.
Common pitfalls to avoid
Many RWAs install rainwater systems but don’t maintain them, which defeats the purpose. Some common mistakes include:
- Neglecting cleaning causes blockages.
- Using unauthorized borewells for recharge invites legal trouble.
- Forgetting to maintain overflow systems causes flooding during heavy rain.
- Poor documentation makes it hard to prove compliance.
Avoiding these ensures your system works well and your society stays clear of penalties.
What happens if you don’t comply?
The consequences can be serious. CMWSSB has the authority to disconnect the water supply if your society fails to install or maintain rainwater harvesting systems. Fines and legal notices may follow, and the society’s reputation and property values can take a hit.
On the flip side, compliant societies often see benefits like reduced water bills and a better standing in the eyes of residents and buyers.
To dive deeper into each specification and ensure your society meets all CMWSSB standards, check out the detailed guidelines available here.