Talking to the rain man

It’s that time of year when we should start worrying about our rain water harvesting systems and get them ready for the coming rains. Dr. Sekhar Raghavan, RWH pioneer, Chennai’s rain man, and the director of the city-based Rain Centre shares some tips

July 25, 2014 05:48 pm | Updated 05:48 pm IST - Chennai

SHOWING THE WAY SekharRaghavan

SHOWING THE WAY SekharRaghavan

What common problems can be expected in RWH structures?

The main hurdle to RWH is the deposit of silt picked up by rainwater from dirty rooftops and driveways. So, keep these clean. Take preventive measures — prune tree branches, empty and clean the filters, wash, dry and fill them. Check rooftop pipes for leaks and replace where necessary.

Also, on a rainy day, residents should observe the various RWH structures such as filters, recharge wells and pits. If any of them is found to overflow, that is an indication for some maintenance work.

Is there an agency to help residents sort out problems in RWH structures?

Our Rain Centre will be happy to help. We have a team of plumbers, masons and well-diggers experienced in not only cleaning the structures but also in creating new ones. In addition, our Rain Centre is willing to give free advice to all residents who want their RWH system evaluated and want improvements.

How can we use rain water collected on roof tops?

The best way to harvest rain falling on roof tops is to discharge it into an open (source) well through a first flush, rather than a filter. A first flush is a dummy pipe connected parallel to the downtake pipe in which the first rain containing the dirt from the roof is collected. It plays the role of a filter. With this, the quality of groundwater will improve instantaneously. If an open source well is unavailable, direct this water to a recharge well.

In places where water is outsourced even on a rainy day, rooftop water can be collected in sumps for immediate use.

How can we best harvest driveway runoff water?

Harvesting driveway runoff water is as important as harvesting rooftop runoff water, if not more. Unfortunately, many people ignore the former. Driveway runoff can be intercepted near the gate(s) by means of a gutter or speed breaker and put into a recharge well covered with a perforated lid and located nearby.

Why is a recharge well preferred to a recharge pit?

A recharge well to put water back into the soil is an important feature of a complete RWH system. It is made of cement rings, easily available. The diameter of these wells can range from 2.5 feet to 6 feet, with the depth depending on the nature of the soil. A recharge well is better than a recharge pit because it can take in larger quantities of rainwater, and can be de-silted and cleaned easily compared to a pit that cannot be cleaned and will get clogged over the years.

What are some common misconceptions regarding RWH systems?

Many residents make the mistake of filling a RC well with gravel or brick rubble thinking that rainwater has to be filtered before it’s put into the soil. This is wrong. An RC well should be left empty and covered with a thick RCC cover. Residents also imagine that open source wells always have a parapet wall and so cannot be located on the driveway. Open wells without a parapet wall can be created on driveways, at the level of the driveway, without projecting above the surface. These wells are covered by strong, four-inch thick RCC slabs, and can take the weight of vehicles driven over them.

Call the centre at 044-24918415, +91 96770 43869; or mail

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