| S.No. | Field / Checkpoint | Reference | Status |
|---|---|---|---|
| A. RWH REQUIREMENT | |||
| A1 | Plot size + DCR threshold (typically > 100 m² mandatory) Acceptance: Mandatory | Per state DCR | OK NC NA |
| A2 | Catchment area — terrace + open ground Acceptance: Calculated | Per drawing | OK NC NA |
| B. SYSTEM DESIGN | |||
| B1 | Storage tank capacity (typically 10-20 m³ per 100 m² catchment) Acceptance: Per design | Per DCR | OK NC NA |
| B2 | Filter design (sand / charcoal / silt trap) Acceptance: Per drawing | Per spec | OK NC NA |
| B3 | Recharge well / pit + dimensions (typically 1m × 1m × 3m deep) Acceptance: Per drawing | Per DCR | OK NC NA |
| C. INSTALLATION + CERTIFICATION | |||
| C1 | Installation per drawing + photographs Acceptance: Verified | Per drawing | OK NC NA |
| C2 | Compliance certificate by Architect + Engineer Acceptance: Certified | Per DCR | OK NC NA |
| C3 | Submission with OC application Acceptance: Submitted | Mandatory | OK NC NA |
Rain Water Harvesting (RWH) is mandatory for most building permits in India under state Development Control Regulations (DCR). Originally introduced in Tamil Nadu (2003) as a response to groundwater depletion in Chennai, the requirement has now been adopted by all major states: - Maharashtra DCR 2034: plot > 300 m² - Delhi MPD 2021: plot > 100 m² (Group Housing) / > 500 m² (Industrial) - Karnataka KMC + KSPCB: plot > 60 sq m + buildings > 200 m² built-up - Tamil Nadu: all buildings, mandatory since 2003 - Telangana: plot > 300 m² - Gujarat GDCR: plot > 1500 m² - Haryana: plot > 100 m²
Without RWH compliance: - Occupation Certificate refused — no OC = no occupancy, no electricity / water connection, no possession - Building completion certificate withheld — RERA registration affected - Penalties under state ground water boards (CGWA national / state-level) - Annual renewal denied for commercial buildings
Governed by Model Building Bye-Laws 2016 (MoUD framework), state DCRs (binding), Central Ground Water Authority (CGWA) notifications + IS 15797:2008 (RWH for storage).
Three components on every project:
A. Catchment + collection: - Terrace runoff calculation: catchment area (m²) × design rainfall intensity (mm/hr) × runoff coefficient (0.85 for tiled / 0.95 for RCC roof) - Open-ground catchment if hardscape > 50% - Down-pipes sized at 100 mm dia for terrace > 50 m² - First-flush diverter (1-2 mm of rainfall diverted to discard) - Leaf / debris screens on all inlets
B. Filtration: - Silt trap chamber — 0.5 to 1 m³ capacity - Sand + charcoal filter — sand (300-500 mm thick) + charcoal (150-300 mm) + gravel layer - Removable / cleanable design (otherwise filter clogs in 2 monsoons) - First-flush diversion ensures clean water enters filter
C. Storage + recharge:
Two options (often combined):
Storage tank for reuse: - Capacity: 5-10 m³ per 100 m² catchment (covers 7-10 day non-rainy period) - Material: PCC / RCC / HDPE / FRP - Used for: flushing, gardening, washing — NOT drinking without further treatment - Pumping arrangement to overhead tank for distribution
Recharge structures for groundwater: - Recharge well (1 m × 1 m × 3 m deep typical) — for soft soils - Recharge pit / trench — for hard rock areas - Borehole recharge (50-100 mm dia bore filled with gravel + sand layers) — for deep aquifers - Sizing rule of thumb: 1 m³ recharge per 50 m² catchment - Distance from sewerage / septic > 5 m to prevent contamination
Documentation for OC submission: - RWH drawing (plan + section + details) - Calculation sheet (catchment area + storage + recharge sizing) - Photographs (during construction + post-completion) - Compliance certificate by Architect + MEP Engineer - Manufacturer's certificates for filter / tank / pipes
1. Token RWH — small recharge pit installed but not connected to terrace down-pipes; checkbox compliance, zero hydrologic benefit.
2. Filter not maintained — installed but no maintenance schedule; clogs in 18 months; system bypassed.
3. First-flush diverter missing — dirty initial rainfall enters tank / filter; contamination + reduced filter life.
4. Recharge near septic — < 3 m distance; groundwater contamination risk; CGWB violation.
5. Tank cover missed — open tank breeds mosquitoes; municipal corporation issues notice + fines.
6. Down-pipes not connected — terrace water bypasses system + drains to street drain; system collecting nothing.
7. Capacity under-designed — 1 m³ tank for 200 m² catchment; overflows in moderate rain; designed for paper compliance.
8. No reuse pump arrangement — storage tank installed but no pump / distribution; water sits unused; eventually drained.
9. Architect certificate without site visit — Architect signs at desk; not visited site; system on paper differs from site.
10. Hard-rock area, deep recharge missed — recharge pit at 3 m depth but aquifer at 30 m; recharge not effective; need bore-recharge.
11. Cross-connection with sewerage — accidentally joined to sewer; sewage backs into tank; serious health risk.
12. No maintenance budget — RMC handed over to society; no AMC for RWH; system dies in 2-3 years.
Companion formats: - Pollution NOC (FMT-STA-006) — environment clearance - Occupation Certificate (FMT-STA-003) — RWH is OC prerequisite - Completion Certificate (FMT-STA-004) - STP Installation Compliance — for buildings > 20 dwelling units - Solar PV Compliance — companion green-building requirements
Codes + Acts: - MoUD Model Building Bye-Laws 2016 — Sections on RWH (Chapter 5) - IS 15797:2008 — Roof Top Rainwater Harvesting — Guidelines - CGWA Notification 2020 — Groundwater Extraction Regulations - National Water Policy 2012 + Jal Shakti initiatives - NBC 2016 Part 9 Section 2 — Plumbing services - CPHEEO Manual — Water Supply + Treatment + Sewerage chapters - State DCRs: - Maharashtra DCR 2034 — Reg 39.3 - Delhi MPD 2021 — Section 4.4.7 - Karnataka KMC + KSPCB Notifications - Tamil Nadu DTCP — 2003 Amendment - Telangana GDCR — Reg 31 - Gujarat GDCR — Reg 17 - GRIHA / IGBC / LEED — green building credit categories for RWH