Rainwater harvesting in apartments

December 26, 2008


Apartments can do with RWH


Huge blocks of flats in cities can provide supplementary water requirement, manage floods and reduce pollution of the environment

Simple techniques: Storing rain and rooftop water in apartments has now become easy

Apartments are mushrooming all over our cities with the boom in the housing sector. These apartments place a huge demand on the infrastructure of the city, be it water, sewerage, stormwater drains or roads. By designing systems carefully and investing in sustainable technologies, apartments can provide supplementary water requirement, manage floods and reduce pollution of the environment.

Consider this large set of apartments in Koramangala which has eight blocks. Six of them have a roof area of 1,000 square metres and two of them have a roof area of 2,000 square metres. The flats are to a large extent dependent on borewells for their water requirement. Car washing in the basement is a significant water consumer. The apartment block wanted to implement a rainwater harvesting scheme to get enough water for the car washing purpose.

Rooftops are ideal catchments for rainwater. If they are clean and allow rainwater to runoff to the down pipes, it is more than enough. In these apartments, the rooftops were ideal catchments.

Down pipes bring the rainwater to the stormwater drains. They should ideally be separated from the sewage and grey water lines. The National Building Code recommends that rainwater pipes be separate from other waste water pipes to prevent overflowing manholes and also to prevent overload of the sewage treatment plants. Many apartments, due to faulty design, tend to merge the two. Here the case was exactly this. The rainwater pipes therefore had to be de-linked from the sewage pipes.

The down pipes were now connected to large rain barrels of 10,000 litre capacity in the basement. The harvested rainwater is to be used for car washing, gardening and other non-potable use. A total of 1.75 million litres of water annually is expected to be harvested from one block alone. Similarly, the collection process has been expanded to another block and in a phased manner will cover all blocks.

When the entire rooftop rainwater collection is put in place, the apartment will harvest 8.75 million litres annually from the rooftops alone.


The stormwater drainage network was found full of garbage and dirt. Regular cleaning will ensure that a substantial amount of storm water too becomes harvestable either to be stored or to be recharged into the aquifer.

Another set of apartments on Bannerghatta Road had not only kept the rooftop clean but also had ensured that the rainwater pipes were kept separate from sewage lines, connected and brought to one place. With a filter, the collection of rooftop rainwater into a 20,000 litre tank became very easy. When the rainwater quality was tested, it was actually found to be of potable standards. This apartment therefore decided to connect the rainwater tank to the regular sump and use the combined water for all purposes. With a 20,000 litre rainwater collection sump and a recharge well for the overflow, the apartment now collects or recharges 550,000 litres of rainwater annually.

Apartments can supplement their water requirement and increase the life of their borewells through smart designs and rainwater harvesting. They can also prevent urban floods. A system of clear guidelines and implementation skill will increase the sustainability of Bangalore’s waters. In this path is water wisdom.


Ph: 080-23641690



  1. This is extremely interesting stuff. I have been researching RWH for the residential scale for several parts of the world, but this is the first that I’ve seen of this scale.

  2. sir, can u give us sugesstions on making a rain water tank in a big housing complex , i requets u to reply this as we are making a model for our science exhibition

  3. Global warming isn’t something people think about each day, nor do they see how it directly affects them. Your report could
    provide your viewers with tangible evidence about global warming and will have more incentive to do something about it.
    Here is how the report could work. You would show a global satellite image of the world. In order to maximize the effect of the
    report, each report should go from the broad view

  4. architectsban . webs . com

  5. interiordesigenrsinbangalore.com

  6. sir i want to know the techincal points or procedure for rain water harvesting.

  7. Very cool! It’s great to see that this is being implemented in more than just single family households. Hey, would you mind posting this on our community rainwater harvesting site? There are lots of people who would really be interested in this post. The site is http://www.waterharvestonline.com, I would really love it if you joined as well to encourage others in our pursuit for a more water conscious world. Thanks and keep up the great posts!

    • Thank you for your comments You are welcome to check the channel zenrainman on youtube which has many small videos on rainwater harvesting, greywater reuse and ecosan. Have also joined waterharvestonline and posted two threads regards V.

  8. […] installation of your new system and cultivating a taste for conservation. So whether you live in an apartment building or an independent home, get […]

  9. I’m researching on various ways to improve tenant relationship vis a vis management companies. At the moment, a tenant find an apartment for rent and the relationship stops there. I’m curious to know what will happen if the apartment locator is able to develop a profound relationship with the management company which he can relate to the future tenant. Any ideas or suggestions will be appreciated.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: