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All you need to know about Rainwater Harvesting

Q: Do you have any water-problem at your home?
A: Yes

Q: Have you heard of Rainwater Harvesting (RWHS)?
A: Yes

Q: Do you think it’s a good way to conserve rainwater for future use, and is good to install?
A: Yes

Q: So you are interested in installing at your house?
A: Hmmmmm…Haven’t thought of it yet, will think and let you know soon.

We all agree to the fact that Water is life, and is essential for survival; and rainwater should be harvested, as it is clean and free natural source of water.

In the scenario of Kathmandu Valley, each and every house has a water-related problem. Some do not have reliable tap-water supply, some don’t have groundwater source, and some have to buy tanker throughout the year, while some have no storage tank.

When it comes to Rainwater Harvesting, almost all have partial to good idea about the system, and many does rainwater collection via themselves (unsystematically), by collecting it in vessels/buckets; for using it for cleaning, washing etc. signifying their knowledge about the importance of free and effective water-source i.e. rainwater.

Though most of the people show interest in installation, yet they have lot many queries regarding it.
Few of the FAQs and their answers:

  1. What is the cost for installation of RWHS?

The cost of installation depends upon the catchment area (the area via which rainwater can effectively be collected) of the house. The starting cost of RWH filter is around Rs. 25,000 (exc VAT) and goes up to 60,000, which is approx cost of a smart-phone, which nowadays every individual carries. Cost of pipes and gutters range depending on the site.


  1. How much rainwater can be collected by the RWHS?

In Kathmandu Valley, more than 36,000 liters of rainwater can be effectively collected from the house built on 1 aana (with roof-size of around 340 sqft). Bigger the roof-size; more is the amount of rainwater collection. A typical house of 3.5 anna can collect more than 120,000 liters of rainwater.


  1. I also collect rainwater, so why should I install the system?

Our system is a very systematic, where the dust particles and the debris are first flushed out, and only then is the rainwater is filtered via our RSF (fully biological process, without any chemicals), and then directed to the existing reservoir tank. Our system is efficient in collecting more than 80% of rainfall falling into the roof via proper piping system, resulting in effective collection.


  1. What do I do with the excess rainwater, during heavy rainfall?

If the rainwater collection is excess than the storage capacity, the overflow rainwater will be directed to the well via reservoir tank (for recharging groundwater), in turn helping maintain the well-water level.


  1. Rainwater tends to attract insects very often. Can the system deal with this? If yes, how?

The water collected via Rapid Sand Filtration (RSF) filtration is free of the debris, droppings and other environmental contamination. Thus once stored in a proper sealed reservoir, the water will not attract insects and can be stored for months.



  1. RWHS is only for rainy season (i.e. 3-4 months), what about other months?

The data of last 20 years shows that Kathmandu Valley receives rainfall throughout the year. The intensity of the rainfall differs and is more concentrated in the months of June to September. Thus the maximum rainwater is collected during the rainy season. During April to June, which are the driest months of supply (municipal) and lowest groundwater levels – nearly 45,000 liters of rainfall is available. That is about six 8000-liter tankers, or more than 12,000 rupees of savings.

Excess rainwater can be recharged into the shallow aquifer completing nature’s cycle – if done collectively on scale this can replenish wells in the area adding dry season supply as well.


  1. Why to install RWHS, if it cannot fulfill my year-round demand? (and I still need to buy water from other sources, even though having RWHS installed)

Yes, we don’t say that RWHS can completely cover the water-demand throughout the year, but it can certainly cover around 60-75% of the water-demand, thereby saving good amount of money, which is being spent on other water-sources.


  1. How much space is required for the installation? What if I don’t have adequate space for installation?

All the RWHS needs is the appropriate piping, and space for a small tank (with filter media i.e. Rapid Sand Filter). For houses that do not have much space, our rainy-filter is very suitable, as it is a compact system that can be wall mounted.


  1. Can collected rainwater be used for drinking/cooking? (as the roof has lots of dust which gets mixed with rainwater)

Yes, rainwater can be effectively filtered (via RSF) for using for utility purposes, such as cooking, gardening etc. and after one more step of filtration (like candle filter etc.), it can also be made drinkable. SmartPaani has small biosand filters and Tripti filters available for this purpose as well.


  1. What if I don’t have underground reservoir tank?

Even if the client does not have an underground reservoir tank, the rainwater can be effectively stored in on-ground tank, for future use.


  1. What is the minimum amount of land required for installing RWHS?

There is nothing such as minimum amount of land required for installing RWHS; but bigger the catchment area, higher will be the amount of collected rainwater.


  1. How hard is maintenance of the system? How much will it cost for maintaining the system?

SmartPaani systems require fairly low maintenance. SmartPaani provides three free maintenance visits, covering a year, with every new installation. During these visits, the technicians empower the client with the required knowledge to maintain the system on their own.


Harvest rainwater, it’s free water-source.

Visit our website ( for more details.

You can also contact us @ 5261530/5260506.


*RWHS: Rainwater Harvesting System

*RSF: Rapid Sand Filter




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