The 2001 edition of IS 14961 offers detailed guidance for establishing rainwater harvesting systems in mountainous regions, specifically through rooftop water collection methods. It covers the aspects of design, selection of materials, installation practices, and maintenance procedures to maximize water harvesting in areas where groundwater and surface water are scarce. This standard is vital for professionals engaged in sustainable water resource management in elevated and semi-arid zones.
Overview
The 2001 edition of IS 14961 offers detailed guidance for establishing rainwater harvesting systems in mountainous regions, specifically through rooftop water collection methods. It covers the aspects of design, selection of materials, installation practices, and maintenance procedures to maximize water harvesting in areas where groundwater and surface water are scarce. This standard is vital for professionals engaged in sustainable water resource management in elevated and semi-arid zones.
Audience
Contents
Structure
This section outlines the extent of IS 14961, focusing on rainwater harvesting in hilly areas through roof collection, and references various Indian Standards relevant to materials and testing methods. It includes material specifications for galvanized steel sheets, mild steel tubes, corrugated aluminium, iron pipes, polyethylene tanks, and guidelines for site selection in hill regions. Additionally, it prescribes rounding procedures aligned with IS 2:1960 to maintain precision in calculations.
This part lists the crucial Indian Standards that IS 14961 incorporates, such as IS 277 for galvanized steel sheets, IS 1239 for mild steel tubes, IS 1254 for aluminium sheets, IS 1536 for cast iron pipes, IS 4984 for HDPE pipes, IS 12701 for polyethylene tanks, and IS 14243 (Part 2) for site selection criteria in hill areas. It also emphasizes adherence to IS 2:1960 for numerical rounding to ensure uniformity.
While an explicit terminology section is not present, this clause clarifies that definitions and terms are consistent with the referenced IS codes for materials and components. Numerical results should be rounded as per IS 2:1960. The terminology aligns with the International Classification for Standards (ICS) related to building materials and structural steel.
This section describes the roof as the principal catchment surface and introduces the fundamental formula for estimating harvested rainwater volume: V = A × R × C, where A is the roof area, R is rainfall depth, and C is the runoff coefficient. It details typical runoff coefficients for various roofing materials, system components such as gutters, downpipes, first flush diverters, and storage tanks, and design principles including slope requirements, debris screening, and overflow provisions.
Defines the roof’s plan area as the effective catchment surface for rainwater collection. It reiterates the volume calculation formula and provides typical runoff coefficients according to roofing types. Emphasizes regular cleaning and maintenance of rooftops to prevent contamination, referencing figures for collection system layouts.
Outlines major system components including the roof catchment, gutters, downpipes, first flush devices, filters, storage tanks, and overflow arrangements. Provides design considerations, typical runoff coefficients for various roofing materials, and guidance on tank sizing based on water demand and rainfall patterns.
Details suitable roofing materials such as galvanized iron sheets, corrugated aluminium, concrete tiles, slates, and thatched roofs with waterproof membranes. Notes the importance of using non-toxic paints and maintaining roof integrity for safe water harvesting. Provides runoff coefficients specific to these materials and references relevant IS codes.
Describes appropriate gutter materials including galvanized iron sheets, wood, bamboo, and reinforced cement concrete. Specifies design considerations such as corrosion resistance, sizing based on roof area and rainfall intensity, and a minimum slope of 1%. A formula for calculating runoff volume through gutters is provided along with typical dimensions.
Lists suitable materials for downpipes such as galvanized mild steel, cast iron, and HDPE pipes with corresponding IS standards. Covers sizing, thickness, slope requirements, and secure installation to withstand environmental loads, supported by typical pipe dimensions.
Explains types of tanks—underground and overground—with materials including masonry, RCC with waterproof lining, galvanized iron sheets, HDPE, and ferro-cement. Details design requirements like location stability, sizing based on demand and rainfall, inlet screens, contamination prevention, filter media, manhole dimensions, overflow and drain provisions, and maintenance protocols.
Summarizes applicable referenced standards for materials and components, emphasizes numerical rounding rules per IS 2:1960, and ensures compliance with testing and quality control as integral to IS 14961.
Highlights critical design factors such as installing tanks on stable slopes following IS 14243 guidelines, determining tank size from water demand and rainfall data, specifying component dimensions, ensuring water quality through first flush diversion and filtration, and prescribing construction and maintenance practices for underground and surface tanks.
Provides instructions for selecting installation sites with slope stability considerations, sizing tanks, installing downpipes with debris screens, incorporating first flush systems, utilizing appropriate filter media, and tank positioning. Emphasizes cleaning and disinfection routines, drainage for slope protection, and key dimensional criteria for system components.
Lists members of the Hill Area Development Engineering Sectional Committee including experts from academia, government, research institutions, and industry. Reiterates design requirements like tank location, sizing, contamination prevention, filter media, tank construction, and maintenance, alongside a summary table of tank features and a schematic diagram of rainwater collection components.
Frequently Asked
IS 14961 recommends using roofing materials with smooth, non-toxic surfaces to ensure clean water collection in hilly areas. Commonly preferred materials include galvanized iron or aluminium sheets due to their durability and effective runoff characteristics. Concrete roofs and clay tiles are acceptable if properly sealed and maintained. Thatched roofs require waterproof coverings such as food-grade low-density polyethylene films. It is essential to avoid materials that may leach harmful substances and to maintain adequate roof slope and first flush systems for water quality.
According to IS 14961, gutters and downpipes should be constructed from corrosion-resistant, non-toxic materials like galvanized iron sheets (as per IS 277), mild steel tubes (IS 1239), cast iron pipes (IS 1536), or HDPE pipes (IS 4984). They must incorporate screens or leaf guards to prevent debris ingress and be kept clean. Roof surfaces should avoid toxic paints, and thatched roofs must be waterproofed properly. Proper slope and sizing ensure efficient drainage, minimizing stagnation and contamination risk.
IS 14961 outlines that underground tanks can be built from masonry or reinforced cement concrete with waterproof linings, or prefabricated HDPE tanks complying with IS 12701. Overground tanks may utilize galvanized iron sheets (IS 277), RCC, plastic or HDPE tanks, or ferro-cement. Materials should be durable, corrosion-resistant, and water-tight. Proper waterproofing and adherence to relevant IS codes ensure longevity and water quality.
Though IS 14961 does not detail the first flush system explicitly, standard practice involves installing a first flush diverter at the downpipe to divert the initial volume of runoff—containing dust, bird droppings, and debris—away from the storage tank. This diverted water is collected in a separate chamber sized to hold approximately 0.2 to 0.5 mm rainfall equivalent and slowly drained after rain events. This process significantly reduces contamination and enhances the quality of stored rainwater.
IS 14961 mandates that tanks be placed only on structurally stable slopes. If instability is detected, safety measures consistent with IS 14243 (Part 2) must be applied. Tanks should be mounted on raised platforms (for surface tanks) to prevent ground movement effects, and underground tanks must be waterproofed to avoid leakage that could undermine slope integrity. Proper drainage systems must be in place to safely channel excess water away, preventing erosion or slope failure.
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