YES! A single person in Malaysia definitely can live entirely on harvested rainwater for their everyday needs without needing to compromise even a little bit!

Thanks to NAHRIM who developed the ‘Tangki NAHRIM’ rainwater harvesting tool (which you can download here), we can simulate the amount of rainwater that we can collect and roughly project it’s use over a period of time.

We ran a sample simulation to see if 1 person living in Kuala Lumpur could live entirely on collected rainwater, and the data says “Yes We Can!”

Here are some parameters that we used for the simulation:

  • the simulation tool only has rainfall data from 1986 to 2006 but the Malaysian rainfall pattern is fairly similar every year
  • we modeled the typical water consumption of a Malaysian which is about 210 litres per person per day (which is 27% higher than the United Nation’s recommended usage of 165 litres per person per day)
  • we referenced a Domestic Water Consumption Study done in 2007 by the Ministry of Natural Resource & Environment to get the water usage breakdown as per the diagram below:

Here is a step by step look at the simulation tool and the results.

Step 1: Select the closes rainfall station to your location

Step 2: You can view the detailed rainfall data by month for any given year

Step 3: Provide details about your roof length and width. You can keep it simple by just entering the length and width of your home as a typical terrace house will be covered from front to back by the roof. If you are calculating for an open tank or any other type of catchment device, you can just adjust the values to get the right ‘Area’ size. The first flush is the initial amount of collected rainwater that is discarded as explained in the previous article here.

Step 4: Enter your daily water usage numbers. You can be specific if you know the details of how much you use for each item. If not, just take the Malaysian average of 210 litres per person per day.

Step 5: Now run the simulation and get the results!

Step 6: Analysis

As you can see, it is possible to live entirely in harvested rainwater without ever needing any additional top-up from the mains. This is an ideal simulated scenario. For a real life example, you can checkout the previous article here.

So download the tool, here is the link again: Tangki NAHRIM and experiment with your own setup. You may have a large family, a small house or an entirely different water usage pattern all together but don’t let that stop you from starting!