Rainwater harvesting in apartmentsDecember 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.