#ConserveWaterMonth Rainwater Harvesting – All Your Questions Answered


Image Source: Author’s Own

Why Should We Save Water?

One in seven Indians does not have access to fresh water. Only 1 percent of all water in the planet is fresh water, the rest being majorly sea water, which is not drinkable. At present, water bore wells are getting deeper, to the extent that in some places in Hyderabad and Bangalore, the water levels have dropped to below 1000 feet. Compare them to the earlier numbers of 300 to 500 feet a decade back and you will understand how much water depletion has occurred. Already, many places are dependent on water that is transported through tankers, and this scarcity is only going to increase with increase in urbanization.

What Is Rainwater Harvesting? How Much Water Can I ‘Harvest’?

Rainwater harvesting is the process of collecting and storing rain water that falls on our roofs. The amount of water you can harvest depends on the amount of rainfall your area receives and the storage space you have. Ideally, in most parts of India, you can get most of your water requirement needs met through rain water. In places such as Bangalore where rains are spread throughout the year, you can even live completely on rainwater.

According to the Brihanmumbai Municipal Corporation (BMC), if 70 percent of the rain falling on 70 percent area of the city is conserved, around 500 million litres can be supplied per day. The BMC currently supplies 3000 million litres a day.


Image Source: Wikipedia Commons

Does It Work Only During The Monsoons? Will I Be Able To Use The Water Later When There Is A Scarcity?

For direct consumption, you can use rainwater only during the monsoons. You can store rainwater for a few days if you have a huge storage tank.

It is important to recharge ground water with rain water so that your bore well or open well water doesn’t dry out during the dry seasons.

What Is Ground Water?

Ground water is the major source of water in most places. It is actually the rain water that is absorbed inside the earth’s surface, which is like a huge water storage area. The top soil is porous, which means it soaks in water that settles down once it reaches the level of impermeable rocks. This natural underground storage is called an aquifer. This is the water which is pumped out by digging bore wells on these surfaces.


Recharge Well – Similar To Open Wells. Image Source: YouTube

Where Can I Store Rain Water?

You can store rainwater in tanks, barrels or let it go down an open well, bore well or a soak pit to recharge ground water levels in your area. You can also connect it to your existing underground storage tank (sump).


Image Source: Flickr

Is There Any Setup Required?

Yes, you need a pipe and a filter from your roof to the rainwater storage barrel or tank placed on the ground. You can connect the existing storm water drainage pipe if it carries only rainwater.

How Much Space Is Required?

The simplest storage solution is to connect the rainwater pipe to a barrel or tank. If you want to use rainwater for everything, you will need a bigger storage, ideally 5 to 10 times the capacity of your overhead tank, almost the space required for a small car. It is better to make an underground tank for rainwater storage. Connecting to an existing well or bore well doesn’t require any additional space.

Do I Need A Special Type Of Filter?

You can use a simple screen filter (a muslin cloth or a mesh grill) if your roof is relatively clean. But ordinary filters can get clogged and would require cleaning. Instead, you can use simple filters made specially for rainwater harvesting. They take in water, filter it and pass cleaned water, and reject a small amount of water with debris, dust and leaves. This design keeps the filter maintenance-free.

How Does It Work?

Rain falls on your roof, gets transferred through the pipe, is filtered and fed into your storage tanks. You can pump this water through your pipes or simply take it through buckets and use it in your garden, wash your car, etc. If you have connected it to your well or bore well, you do not have to do anything different.

How Much Would It Cost?

A rainwater harvesting filter costs around INR 2000 to 6000 depending on the flow rate. A bigger terrace would need a bigger filter. Piping work would cost around INR 1000 to 5000 depending upon the length required. A barrel costs around INR 300 to 500, a 1000 litre plastic (Sintex) tank costs around INR 3500. Bigger storage would cost more.


Rainwater Storage Tank. Image Source: Wikipedia Commons

What All Can The Water Be Used For? Is Rainwater Safe To Drink?

Rainwater is naturally filtered, but there is a chance of contamination from the surface it falls on. Also, if the air is severely polluted, the water may be acidic. Rainwater can safely be used for washing, flushing and cleaning without treatment. To make rainwater potable (good enough to drink), you can connect it to your water purifier and use it. Chennai has been doing so for the past three years. It is highly recommended that you test the water before you consume it. Water testing is done at labs in your water supply department and also at water purifier company labs such as Eureka Forbes.

What Benefit Will I Get If I Recharge Ground Water?

Your bore well will never become dry and ground water level will increase in your area. Some high rises dig deep bore wells and water in the surrounding area falls down. This can be prevented with rainwater recharging. Also, it will help to prevent flooding of streets due to over flowing of storm water drains. Another major benefit is that the water doesn’t get contaminated.

What’s The Best Combination?

An underground storage tank with a capacity to store water for a few days, and the excess fed into a well to recharge the ground water.

Can I live Completely On Rainwater Without Any Other Water Supply?

Yes, if you plan well. It also depends on your area’s weather. The biggest challenge is to collect enough rainwater for the dry seasons. This is easier in areas where rainfall happens throughout the year (for example, Bangalore). Build storage tanks wherever you can, under your garage, garden, everywhere. An open traditional well dug deep is a good alternative if you can’t make enough tanks. An open well will store a good amount of water and also recharge the ground water. Ground water is the biggest storage.

Reuse every bit of water and reduce consumption by installing low flow taps and showers. Low flow taps and showers, available at most plumbing stores, restrict water flow and some add air to the water to form a ‘foamy’ output which saves water.  Waste water from washing clothes can be used for flushing, and water from baths can be used in the garden. This water is called ‘grey water’. Grey water needs to be collected in a separate tank and pumped back through separate pipes. There are ways to treat grey water and make them potable too. Water from the kitchen can be used to water your plants. It is better to connect separate pipes and small tanks, one for kitchen, one for the bath water in bathrooms, and one for the washing machine.

Are There Any Official Guidelines For It?

Yes, check with your municipal corporation before starting work on rainwater harvesting. It is mandatory in Bangalore, Pune and Chennai. In Karnataka, rainwater harvesting is required by law for rooftop sizes greater than 2400 square feet. In Chennai, all buildings over 3 stories high, irrespective of roof size are required to have rainwater harvesting systems. You will not be given sewage and water lines unless you have installed rainwater harvesting systems.


Rainwater Harvesting In A Bangalore Apartment. Image Source: Author’s Own

Have People Started Doing It Already? What Are The Results?

Yes, rainwater harvesting is mandatory in many places in India and in fact, severely affected areas have shown great improvement in water levels. There are people in Bangalore who live completely off rainwater. In Chennai, after the frequent water crisis, rainwater harvesting was made mandatory in 2001. Today, there are more than 5,00,000 buildings connected with rainwater harvesting systems and the city has now recovered from the water deficit. The state of Tamil Nadu has more than 22 lakh buildings fixed with rainwater harvesting systems.

Does Government Provide Any Subsidies?

The Karnataka Government gives a rebate of 5 to 10 percent on water bills for homes implementing rainwater harvesting. Odisha is planning to give a subsidy of 50 percent (a maximum of INR 45000) on the capital cost of setting up a rainwater harvesting system on roofs that measure more than 2100 square feet.

If I Want To Start With Rainwater Harvesting, Who Should I Contact? Are There Agencies Or Experts For It?

You can contact local rainwater harvesting contractors or your local water supply authorities for more details. There are many companies and consultants involved in rainwater harvesting. A quick look through your classifieds will get you contacts. The Bangalore Water Supply and Sewerage Board has details that lists authorized suppliers and contractors. There is a ‘Rainwater Club’ based in Bangalore. In Mumbai, you can contact the RainWater Harvesting Cell in the BMC (tel. 022 – 22620251 ext.2309).

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