- A rainwater harvesting system collects rainwater from your roof and either stores it for household use or recharges groundwater, reducing dependence on municipal and tanker water.
- The installation process includes planning the water flow, installing gutters, filters, and first-flush diverters, and connecting either a storage tank or a recharge pit based on your needs.
- A home rainwater harvesting system typically costs ₹ 8,000 to ₹ 1,00,000+, depending on the system type, roof size, storage capacity, filtration components, and installation requirements.
Rainwater harvesting is collecting and storing rainwater rather than allowing it to flow away. In the majority of domestic buildings, rainwater is collected from the roof with the help of gutters and pipes and is either stored for future use or allowed to recharge the groundwater. This guide will explain how rainwater harvesting works along with the various types, components, installation, and cost of harvesting rainwater.
What is Rainwater Harvesting?
Rainwater harvesting, the practice of gathering and retaining rainwater rather than allowing it to run off. In the majority of households, rainwater is collected from the roof using catchment tanks and piping, for later use or pumped into the ground for recharging. The two main purposes of a rainwater harvesting system are:
- Storage : Gather rainwater in a water tank for future use like gardening, washing cars, and other household purposes (drinking if treated properly).
- Groundwater recharge : Direct rainwater to recharge pits, trenches, or wells to restore groundwater levels.
Rainwater harvesting is gaining more importance in India. While the monsoon brings a lot of rain to the country, most cities have water shortages in the remaining months of the year, and groundwater levels are also dropping. Thus, many states and cities have mandated new buildings to have rainwater harvesting systems.
How a Rainwater Harvesting System Works
The principle behind the rainwater harvesting system is to collect rainwater from rooftops and other surfaces, purify it, store it for future use, or direct it to the ground.
- Catchment (Roof/Terrace): The surface including the roof or terrace on which the rainwater initially falls and is gathered. Well-maintained and clean roofs help collect better-quality rainwater.
- Gutters & Downpipes: These are installed around the edges of the roof to catch rainwater, and it flows from the roof through the downpipes safely into the filtration system.
- First-Flush Device: This device channels off the first few minutes of rainfall as it cleanses the roof of dust, leaves, bird droppings, etc which are trapped between rains.
- Filter: The filter is constructed after the first flush is diverted. It filters the collected water to remove fine dirt.
- Storage Tank or Recharge Pit: The filtered water is stored in a storage tank or is pumped into a recharge pit or borehole where it slowly filters down to the groundwater.
Types of Rainwater Harvesting (Storage vs Recharge)
Rainwater harvesting systems are divided into two types: storage systems and groundwater recharge systems.
1. Storage System
Choose a storage system if you need rainwater for regular use. It collects filtered rainwater and holds it in tanks. The stored water can be used for various purposes like gardening or drinking after treatment.
2. Groundwater Recharge System
A groundwater recharge system is a better option when you want to revive a borewell or meet local rainwater harvesting needs. Recharge systems are budget-friendly to install and require less maintenance as they do not need a large water storage tank.
| System Type | What It Does | Best For | Key Components |
|---|---|---|---|
| Rooftop Storage | Stores filtered roof rainwater in a tank for direct use | Homes looking to reduce municipal water or tanker use | First-flush device, filter, storage tank, pump |
| Groundwater Recharge | Directs filtered rainwater into a recharge pit or borewell to replenish aquifers | Homes recharging borewells or meeting local regulations | Recharge pit/well, gravel, sand, filter media |
| Combined (Storage + Recharge) | Stores usable water and recharges excess rainwater | Most homes; the recommended long-term solution | Storage tank, filter, first-flush device, recharge pit or well |
Rainwater harvesting systems are categorised as active or passive systems.
Active vs Passive Rainwater Harvesting:
- Active systems use engineered components like gutters, filters, tanks, and recharge pits.
- These advanced components manage rainwater well.
- Passive systems direct the rainwater into a garden or a soak pit. This allows it to naturally soak into the ground without filtration.
What Are the Main Components of a Home Rainwater Harvesting System?
A home rainwater harvesting system consists of six key parts:
- Catchment
- Gutter and downpipes
- First-flush diverters
- Filter
- Storage tank or recharge structure
- Delivery system
1. Catchment (Roof or Terrace)
The catchment is a roof or terrace surface where the rainwater is collected. RCC and tiled roofs provide a smooth surface for water to flow easily and collect fewer contaminants. These surfaces need less maintenance than roofs covered with moss or dirt.
2. Gutters and Downpipes
Gutters collect rainwater from the edge of the roof. Downpipes carry this water to filtration or recharge systems. Gutters and downpipes should be the right size for your roof and local rainfall to prevent water from overflowing during heavy rain. PVC and UPVC gutters are the popular choices as they are long-lasting and affordable. Read our Plumbing Basics for Indian Homes guide to understand how pipes, fittings, and water supply lines work together.
3. First-Flush Diverter
The first flush diverter will remove the first water that drains off the roof. This water contains dirt. It is an affordable and simple component, but it can make a difference to the quality of rainwater collected.
4. Filter
After diverting first-flush, the rainwater enters the filters. These filters remove silt, leaves, and debris from water before storage or groundwater recharge. You can select a basic mesh filter or sand-gravel filter, or install a packaged rainwater filter.
5. Storage Tank or Recharge Structure
Filtered rainwater can either be stored for later use or directed into the ground.
- Storage Tank: An overhead or underground storage tank stores water for gardening, flushing, and other non-portable uses.
- Recharge structure: A recharge pit or recharge well uses layers of gravel, sand and charcoal to allow filtered water to seep into the ground and recharge groundwater.
6. Delivery (Pump, Pipes, and Tap)
A delivery system distributes harvested rainwater to its intended location. It can be gardens, flushing systems and outdoor cleaning areas in storage systems. This includes a pump and PVC pipes to connect the storage tank to garden irrigation or flushing systems.
How to Set It Up at Home?
- Step 1
- Assess your home
Measure the roof surface area and the mean annual rainfall in your area. You can plan whether you want a storage system or a recharge system. You can also choose a combined system that can store the rainwater and also recharge the groundwater. This can determine the size and design of your system.
- Step 2
- Plan the water flow
Decide where water is going to go: Roof → Gutters → Downpipes → First-Flush Diverter → Filter → Storage Tank or Recharge Pit . Select the lowest and easiest spot for the tank or recharge pit to allow water to flow freely.
- Step 3
- Install gutters and downpipes
Install gutters with a slight slope towards the downpipes along the outer edge of the roof. Make sure they are well arranged and are the correct size for heavy rain to prevent overflow.
- Step 4
- Install the first-flush diverter and filter
Use a first-flush diverter before the filter to remove the first flow of rainwater. The remaining rainwater will then flow through the filter before entering the storage tank/recharge structure.
- Step 5
- Build the storage or recharge system
If you plan on using harvested water, install an overhead or underground storage tank. And if you want groundwater recharge, create a recharge pit or borewell with a layer of gravel, coarse sand, charcoal, and include an overflow outlet to divert extra rainwater. If your home has a basement, read our Basement Waterproofing guide before installing a recharge pit to prevent moisture and foundation damage.
- Step 6
- Connect and test the system
For storage systems, install a pump and plumbing to distribute the collected water. During the first rainfall, check the system for leaks and make sure the first-flush diverter, filter, and overflow system are working properly.
A simple recharge pit can be a good do-it-yourself project (with the assistance of a mason). An entire storage setup that includes plumbing and pumps is best installed by a trained plumber.
Sizing: How Much Rainwater Can You Collect?
A basic formula to know the amount of rainwater that can be collected in a home can be done using: Harvestable water (litres) = Roof area (m²) × Annual rainfall (m) × 1000 × Runoff factor. The runoff factor includes water loss from the first-flush diverter, evaporation and splashing. A runoff coefficient is 0.8 for a smooth RCC roof. Let's take an example of an average home in Bengaluru:
| Input | Example (Bengaluru Home) |
|---|---|
| Roof area | 100 m² (≈ 1,076 sq ft) |
| Annual rainfall | 970 mm (≈ 0.97 m) |
| Runoff coefficient (RCC roof) | 0.8 |
| Harvestable water/year | 100 × 0.97 × 1,000 × 0.8 = 77,600 litres |
A small 100 m² roof in Bengaluru city can capture approximately 77,600 litres of rainwater annually. This will help you to save a lot on water bills and municipal water or water tankers. These are approx. calculations as of 2026. The actual amount of water collected depends on your roof material, first-flush losses, and how well the system is maintained.
Cost of a Home Rainwater Harvesting System (₹)
A house rainwater harvesting system can cost between ₹8,000 and ₹1,00,000+. The cost will depend on the type of system and roof size. These are approximate figures as of 2026 and can differ from city to city and supplier to supplier.
| System | What It Includes | Indicative Cost (₹) |
|---|---|---|
| Basic Recharge Pit | Recharge pit, filter media, gutter connection | ₹8,000 to ₹25,000 |
| Small Rooftop Storage System | First-flush diverter, filter, 1,000-2,000 L tank, pipes | ₹15,000 to ₹40,000 |
| Full Storage + Recharge System | Storage tank, recharge pit/well, filter unit, pump, plumbing | ₹40,000 to ₹1,00,000+ |
Systems with advanced filters and underground tanks for larger homes usually cost more. However, a well-designed system can help save money over time by reducing water costs.
These are 2026 estimated prices only and may differ from area to area, house to house and the cost of materials. When deciding, always get a site inspection and quotation.
Is Rainwater Harvesting Mandatory in Bengaluru?
Yes. Most residential properties above a minimum plot size are subject to regulations by the Bangalore Water Supply and Sewerage Board (BWSSB) and civic requirements. New properties measuring 1200 sq ft or more require a rainwater harvesting system. Otherwise, extra water charges or penalties are imposed on these properties. Make rainwater harvesting a long-term investment rather than a mere legal obligation.
Maintenance and Water Quality
- Clean gutters and downpipes before and during the monsoon to get rid of dirt.
- Wash the first-flush diverter and filters often to prevent contaminants from entering the system.
- Inspect and de-silt recharge pits often to maintain proper groundwater recharge.
- Keep storage tanks covered to prevent algae growth or debris from direct sunlight.
- Check tanks, pipes, and fittings for leakage or damage, especially after heavy rainfall.
- Treat harvested rainwater before drinking by using filtration or a boiling process. If untreated, use it only for non-drinking uses.
- Use harvested rainwater for household cleaning purposes or gardening as it is naturally soft and suitable for these applications.
- Schedule a complete system inspection every year to find worn components and ensure a good performance before the rainy season.
Benefits of Rainwater Harvesting
- Reduces water bills: Reduces reliance on municipal water and private water tankers with an extra source of water.
- Recharges groundwater : Can help restore groundwater tables, which may be reduced due to borewell reduction.
- Reduces urban flooding : Redirects the rainwater before it flows into storm drains, minimising run-off and waterlogging during the heavy downpours in Bengaluru.
- Provides soft, chemical-free water : This is perfect for all your household needs and will help to minimise the use of soap and the occurrence of hard water stains.
- Supports regulatory compliance : Helps meet local rainwater harvesting requirements and makes the water supply more sustainable at your home.
Frequently Asked Questions
How does a rainwater harvesting system work?
Rainwater harvesting systems gather rainwater from your roof, transfer it through rainwater gutters and downpipes, filter out debris with a first flush device and filter and send it to a rainwater storage tank for reuse or a recharge pit to replenish the groundwater.
What does a home rainwater harvesting system cost in India?
The price range for a simple home rainwater harvesting system in India is ₹8,000 to ₹1,00,000+. A small rooftop storage setup can cost ₹8,000 to ₹40,000. The entire system will cost you a minimum of ₹1,00,000 for a full storage and recharge system.
Is rainwater harvesting mandatory in Bengaluru?
Yes. It is mandatory to set up rainwater harvesting systems in Bengaluru. The Bangalore Water Supply and Sewerage Board (BWSSB) requires eligible residential and commercial properties with a site area of 1200 sq ft or more to install rainwater harvesting systems.
Which should I choose: Storage or recharge?
Choose storage if you want to use rainwater for gardening or household needs. Choose recharge if you want to refill groundwater and improve borewell performance. Many homes benefit from a combination of both systems.
How much rainwater can I collect from my roof?
You can estimate roof rainwater collection using the formula: Roof Area (m²) × Annual Rainfall (m) × 1,000 × Runoff Coefficient. For example, a 100 m² (≈1,076 sq. ft.) RCC roof in Bengaluru receiving 970 mm of annual rainfall can harvest about 77,600 litres of rainwater per year, assuming a runoff coefficient of 0.8.
Is harvested rainwater safe to drink?
Yes, but only after proper treatment. Harvested rainwater should be filtered and disinfected before drinking. Without treatment, it is best used for non-potable purposes such as gardening or cleaning.
Find the Right Rainwater Harvesting Essentials with HomeRun
The easiest thing to do for water efficiency is to collect rainwater. With proper storage, recharge or hybrid systems, water bills can be lowered, groundwater can be recharged, and a reliable water supply can be provided that will yield long-term benefits in a water-stressed city. HomeRun offers various water harvesting essentials. Order 100% original pipes, filters, storage tanks and RWH fittings and get them delivered in 60 minutes to your doorstep.