Mandate guide · Karnataka
Is rainwater harvesting mandatory in Karnataka? Yes, since 2009.
Karnataka — and specifically Bangalore via BWSSB and BBMP — has had a mandatory rainwater harvesting regime since 2009. Compliance is a precondition for receiving an occupancy certificate on new construction and for retrofitting older properties above a size threshold. Non-compliance attracts a fine of up to ₹5,000 plus a 50% surcharge on the water bill until the system is in place. This guide covers exactly who must comply, what counts as a compliant system, and how to file the paperwork with BWSSB.
Quick answer
Mandatory for new buildings on plots of 30 ft × 40 ft (1,200 sq ft) or larger built after 2009, and for existing buildings on plots of 60 ft × 40 ft (2,400 sq ft) or larger built before 2009. The system must provide at least 20 litres of storage or recharge per m² of roof area, plus 10 litres per m² of paved open space. Enforced by BWSSB; non-compliance is fined up to ₹5,000 and triggers a 50% water-bill surcharge.
Who must comply
| Building type | Size trigger | RWH required? |
|---|---|---|
| New residential construction (post-2009) | Plot ≥ 1,200 sq ft (30 × 40 ft) | Yes — required for occupancy certificate |
| Existing residential building (pre-2009) | Plot ≥ 2,400 sq ft (60 × 40 ft) | Yes — retrofit mandatory |
| Residential plot below threshold | < 1,200 sq ft (new) / < 2,400 sq ft (existing) | Voluntary but recommended |
| Commercial / institutional | All sizes | Yes — mandatory irrespective of plot size |
| Apartment / housing society | All plots ≥ 1,200 sq ft | Yes — RWA / builder responsibility |
What “compliant” means
BWSSB defines a compliant system in volumetric terms. Your roof catchment area drives the minimum storage or recharge capacity, and the paved area around the building has its own provision. Both storage tanks and groundwater recharge structures are recognised — most installers default to a hybrid (storage for non-potable use plus recharge for groundwater contribution). The first-flush diverter and a multi-stage filter (typically sand + activated charcoal, or a modular cartridge) are integral parts of the system, not optional add-ons.
- Storage capacity: at least 20 litres per m² of roof area
- Paved area provision: at least 10 litres per m² of paved open space
- Either storage tank for reuse, or groundwater recharge structure (pit, well, trench), or both
- First-flush diverter + filter at the inlet
The paperwork
Step-by-step compliance flow as published by BWSSB / BBMP:
- 1Install RWH system via a BWSSB-trained plumber
- 2Submit self-declaration form to local BWSSB sub-division office
- 3Attach photographs of installed system
- 4Retain a copy of approval for renewal cycles
Official source: BWSSB / BBMP portal · Last verified 2026-05-12
Penalties for non-compliance
Non-compliance is detected during the occupancy-certificate inspection (for new builds) or during a periodic BWSSB audit (for existing buildings). The penalty has two parts: a one-time fine up to ₹5,000 paid to BWSSB, and a recurring 50% surcharge on the water bill that continues until BWSSB verifies the installation. In effect, a typical Bangalore home that previously paid ₹400/month in water bills will pay ₹600/month until the system is installed, on top of the fine. Practical impact: the surcharge alone covers the cost of a basic RWH system in roughly 18–24 months, before counting any tanker-bill savings.
How to install legally
The legally cleanest path is to hire a BWSSB-trained plumber or a vendor on BWSSB's recommended-installer list. They will design a system sized to your roof area, install it with the required components, and help you file the self-declaration form with photographs at your local BWSSB sub-division office. Many installers bundle the paperwork into their service offering — confirm this before signing the contract. For societies and larger plots, BBMP also requires a structural-engineering sign-off on the recharge structure's depth and load-bearing characteristics. Use RainbowHome Water's installer directory to compare BWSSB-certified vendors active in your area, with transparent pricing per square metre of roof area.
Frequently asked questions
I bought my Bangalore home in 2015 — does the mandate apply to me?
If your plot is 1,200 sq ft or larger and the building was constructed after 2009, yes. The original builder should have installed RWH as a precondition for the occupancy certificate. If they didn't, the responsibility transfers to you as the current owner. A BWSSB compliance check during your next water-connection renewal or property-tax update may flag this.
What if my property is in the BBMP area but not on BWSSB supply?
The BWSSB mandate applies to all properties within BBMP limits regardless of whether they currently take Cauvery water or rely on borewell/tanker. The mandate is regulatory (driven by building bylaws), not contingent on being a BWSSB customer.
Can I install a recharge-only system and skip the storage tank?
Yes. BWSSB accepts both pure storage and pure recharge systems as compliant, as long as the volumetric thresholds are met (20 L/m² of roof area for either). Recharge-only systems are cheaper to install but produce no captured-water benefit for the homeowner; they're mandate-compliant but economically less attractive.
How big a tank do I need for a typical 1,500 sq ft (140 m²) Bangalore home?
BWSSB requires at least 140 × 20 = 2,800 L of storage or recharge capacity. Most installers recommend 3,000–5,000 L of storage tank for practical reasons (peak monsoon overflow handling), supplemented by 1–2 recharge pits.
Does my apartment society's existing RWH installation cover me as a flat owner?
Yes, if the society's installation is BWSSB-certified and covers the building's total roof area at the required rate. Flat owners are not individually liable as long as the society/RWA holds the compliance certificate. Confirm this is current with your RWA secretary at AGM time.
What about the BBMP property-tax rebate?
BBMP has periodically discussed (but not consistently enforced) a property-tax rebate for RWH-compliant properties. Check your current BBMP property-tax bill — if a rebate field is missing, ask your local revenue office. The penalty avoidance and water-bill normalisation are the more reliable economic benefits.
Can I claim the RWH installation cost as a tax deduction?
Currently no specific section of the Income Tax Act provides a residential RWH deduction. You may be able to capitalise the cost into your home's cost basis for long-term capital-gains computation, but consult a tax advisor.