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Rainwater Harvesting

Kathmandu Valley receives 1600 millimeters of rain every year. This means that on a typical rooftop of 100 square meters more than 160,000 liters of rain is available for capture and use. Municipal water supply is becoming increasingly inadequate, water quality questionable, and serves under half the demand in Kathmandu. Tanker water trucks are expensive and water quality questionable. Groundwater levels are depleting and quality is becoming increasingly worse.

Harvest rainwater with a SmartPaani system – save water, save money, and recharge wells improving both the groundwater quality and quantity. SmartPaani’s technical team is the most experienced in Nepal with hundreds of installations in Kathmandu Valley since 2007. SmartPaani is constantly working to improve our products and will deliver a quality and reliable system that utilizes this free water falling on the roof.


What is Rainwater Harvesting?

Rainwater Harvesting is the collection and utilization of the rain that falls on rooftops and other surfaces for immediate and future use. This is done either by using storage tanks or recharging the rainwater into underground sources such as tube wells.  SmartPaani’s Team creates custom solutions based on customers' needs and situation. Solutions range from tank-based storage for all uses during the rainy season, groundwater recharge for year-round water supply, or tank storage for year-round drinking and cooking uses. The case studies page illustrates different examples.

SmartPaani Rapid Sand Filters (RSF):

SmartPaani's Rapid Sand Filter is a custom designed rainwater harvesting system. This system  consists of first flush device which flushes out the first ran containing the maximum debris. This is followed by a customized rapid sand filter consisting of layers of filter media which remove the remaining dirt and debris and reduce bacteria from rainwater. The rapid sand filter is sized according to the roof size of the building.

SmartPaani systems come in the following sizes depending on the roof size:

-SmartPaani 200 RSF, 300 RSF, 500 RSF, 750 RSF, 1000 RSF

Each of these Standard SmartPaani System Installation includes the following components:

  • First Flush to clean the roof - this is a manual device that is included in the SmartPaani Rapid Sand Filter package.
  • Rapid Sand Filter for particles and contaminants
  • *Conveyance from roof to tank (gutter, pipes) are extra and depend on the building specifics.

SmartPaani New Rainwater Harvesting Filter System - Rainy Filter:

Rainy filters are designed with self cleaning mechanism and can be fixed to the wall by connecting Rooftop rainwater drain pipes.  The water enters into inlet, rotating slowly along periphery in angular motion at specific velocity, creating cohesive force and segregates dirt particles and clean water individually. However when the intensity of rainfall increases the high volume of water moves in circular motion with high velocity in the upper housing and creates a centrifugal force.

In both situations, involving low and high intensity of rainfall , the working principle of the filter based on cohesive and centrifugal force respectively, aids the filter element to divert clean water into the cistern/ recharging well and simultaneously flushes out automatically sand, debris, and dirt particles through the drain outlet.

Rainy filters come in 4 different types (depending upon its catchment area, inlet size, drain outlet etc.)

FL-100, FL-200, FL-300, FL-500

The rainy season is when the water supply is good, why should I harvest rainwater?

Three reasons:

1) This is not always the case and becoming increasingly less so. The current demand for water is 320 Million Liters Per Day while the supply is only 120 Million Liters a Day in the Monsoon. In 2002 the demand was 140 Million Liters a Day; every day the water situation becomes worse for somebody even in the monsoon, tomorrow that person could be you. More than 15% of Kathmandu’s population purchases trucks of water year round, meaning they spend more than 30,000 rupees a year on water.


2) Convenience; More than half of the people have to get up between 12 and 6 a.m. to deal with water, even during the monsoon. If you use the storage tank in your house to collect rainwater this inconvenience is avoided. Additionally the occasional sewage leaks that affect municipal supply, especially during the monsoon, will no longer be a problem during this time.


3) Groundwater – Most people we talked to used to have abundant water in their tube wells 15 years ago, but do not today. Why? Over pumping – No. The main problem is that the rain that used to go into the groundwater is now sent to the sewer. More rainwater inside the Ring Road is sent to the sewer than the much-hyped Melamchi will provide in a year. 15 years ago this figure was half. Before this water used to percolate into the ground and much of it remained for dry season consumption, this is no longer the case. SmartPaani can work with you to begin to help recharging this “wasted” rainwater into your well.