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IS 16016:2012 is the Indian Standard (BIS) for installation of rainwater harvesting systems in buildings. This code provides guidelines for the planning, design, construction, installation, and maintenance of rainwater harvesting systems in buildings. It details system components such as catchment areas, conveyance systems, filters, and storage tanks to promote water conservation and sustainable water management.
Provides guidelines for the installation of rainwater harvesting systems specifically within building premises.
Overview
Status
Current
Usage level
Frequently Used
Domain
Water Resources — Green Building and Sustainability
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! Always incorporate a 'first flush' diverter to prevent the initial, more contaminated rainwater from entering the storage tank. This significantly improves stored water quality.
! Regularly clean gutters, downpipes, and filter media, especially before the start of the monsoon season, to prevent clogging and maintain system efficiency.
! Verify local municipal regulations, as many now have mandatory requirements for rainwater harvesting in new constructions which may include specific design criteria or subsidies.
BS 8515:2009+A1:2013British Standards Institution (BSI), United Kingdom
HighCurrent
Rainwater harvesting systems. Code of practice
Provides recommendations for the design, installation, and maintenance of RWH systems for non-potable uses in the UK.
CSA B805-18/ICC 805-2018CSA Group (Canada) / International Code Council (USA)
HighCurrent
Rainwater Harvesting Systems
A joint North American standard covering the design, materials, installation, and maintenance of RWH systems.
AS/NZS 3500.3:2021Standards Australia / Standards New Zealand
MediumCurrent
Plumbing and drainage - Part 3: Stormwater drainage
Covers overall stormwater drainage, with a dedicated section on the installation of rainwater tanks and systems.
DIN 1989-1:2002-04Deutsches Institut für Normung (DIN), Germany
HighCurrent
Rainwater harvesting systems - Part 1: Planning, installation, operation and maintenance
A comprehensive German standard for the entire lifecycle of rainwater utilization systems.
Key Differences
≠IS 16016 places a significant emphasis on using rainwater for artificial groundwater recharge (via recharge pits, trenches, borewells), which is a key priority in the Indian context. Most international standards focus primarily on rainwater collection for direct non-potable use (e.g., toilets, irrigation).
≠Water treatment requirements in IS 16016 are generally prescriptive and basic, often limited to first-flush diversion and sand-gravel filters. Standards like CSA B805/ICC 805 have more detailed, risk-based treatment requirements (e.g., specific micron-level filtration, UV disinfection) tied to the intended end-use of the water.
≠IS 16016 provides prescriptive formulas for sizing components and recharge structures based on rainfall intensity and area. International standards often favor a more performance-based water-balance modeling approach, allowing engineers to size tanks based on desired water-saving efficiency and supply reliability.
≠International standards like BS 8515 have very stringent and specific requirements for backflow prevention (e.g., Type AA or AB air gaps) to comply with national water supply regulations, whereas IS 16016's guidance on air gaps is less formally categorized.
Key Similarities
≈All standards identify the same fundamental system components: catchment surface, gutters and downpipes (conveyance), pre-storage filtration, storage tank, and a distribution system.
≈The principle of diverting the initial, more contaminated rainfall (the 'first flush') is a common requirement or strong recommendation across all standards to improve stored water quality.
≈All codes mandate a strict separation between the rainwater system and the potable (drinking) water supply to prevent cross-contamination, a critical public health measure.
≈A universal requirement is the clear and permanent labeling of all rainwater pipes and outlets (taps) to indicate that the water is non-potable and not safe for drinking.
Parameter Comparison
Parameter
IS Value
International
Source
First Flush Diversion Guideline
Divert first 10-20 minutes of rain, or a volume equivalent to 0.5-1.0 mm of rainfall over the catchment area.
Divert a volume equivalent to 1-2 mm of rainfall. Some jurisdictions specify a fixed volume per area (e.g., 40 L per 100 m²).
CSA B805-18 / General Best Practice
Mains Water Top-up Backflow Prevention
An air gap shall be maintained between the potable water inlet and the maximum water level in the tank.
A verifiable air gap (e.g., Type AA or AB as per UK regulations) must be used to prevent backflow into the public water main.
BS 8515:2009+A1:2013
Pipe Identification
Pipes should be marked 'NON-POTABLE RAINWATER'. No specific color is mandated.
Pipes must be colored purple (lilac) or have purple identification tape, and be labeled 'RAINWATER' or 'NON-POTABLE WATER'.
AS/NZS 3500.3:2021 / ICC 805-2018
Pre-storage Filtration
Prescribes physical filters like sand-gravel beds with specific layer depths (e.g., 20-30 cm fine sand, 10 cm gravel).
Specifies performance-based filtration, e.g., a filter with a mesh size of 300-500 microns before the tank.
BS 8515:2009+A1:2013
Tank Sizing Methodology
Based on a formula for total potential harvest: Area x Rainfall x Runoff Coefficient.
Often uses a detailed water-balance analysis, comparing monthly rainfall supply against monthly water demand to optimize size.
CSA B805-18/ICC 805-2018
Tank Overflow Sizing
The overflow pipe should be of the same diameter as the inlet pipe.
Overflow must accommodate the maximum possible inflow from a design storm and be at least the same nominal size as the inlet.
AS/NZS 3500.3:2021
⚠ Verify details from original standards before use
Key Values7
Quick Reference Values
Runoff coefficient for concrete roof0.70 - 0.90
Runoff coefficient for corrugated metal sheets0.70 - 0.90
Runoff coefficient for tiled roof0.75 - 0.90
First flush recommendationDivert first 10-20 minutes of rainfall or 2.5 mm
Recommended pH for harvested rainwater (for non-potable use)6.5 to 8.5
Typical per capita water requirement for storage design135 litres/day
Recommended screen mesh size for inlets1 mm
Key Formulas
Harvestable Water (m³) = Catchment Area (m²) x Annual Mean Rainfall (m) x Runoff Coefficient
Tables & Referenced Sections
Key Tables
Table 1 - Run-off coefficients for various types of roof surfaces
Table A.1 - Typical Rainwater Pipe Sizes for various roof areas
Key Clauses
Clause 4 - Planning and Design Considerations
Clause 5 - Components of a Rainwater Harvesting System
How do you calculate the potential amount of water to be harvested?+
Use the formula: Potential Harvest = Catchment Area × Rainfall × Runoff Coefficient. The Runoff Coefficient is found in Table 1 based on the roof material.
What is a 'first flush' and why is it important?+
It's the first spell of rain that washes off debris and pollutants from the roof. The code recommends diverting it (approx. 2.5 mm of rain) to ensure cleaner water is collected for storage (Clause 5.4.1).
Is filtration necessary for harvested rainwater?+
Yes, a filter is a critical component to remove suspended pollutants like leaves and dust before the water enters the storage tank or recharge structure (Clause 5.5).
Can harvested rainwater be used for drinking?+
Only after proper treatment, including disinfection, to meet the standards of IS 10500. This code primarily covers collection and storage for non-potable uses like flushing, gardening, and washing.