General information

Global volume of fresh water

In 2008 it was recently been reported that South Africa, with half the global average rainfall, will run out of water as soon as 2015. It started happening in small towns across the country and now in 2018 it has happened in a major city like Cape Town. Specialist estimate that South Africa will be short of 3-billion cubic meters of water by 2030 which amounts to 17% of expected demand.
As water resources decline and water quality and reliability of supply become more suspect, more and more people and companies are looking at alternative sources of supply.

Municipla water savings calculator

Most municipalities have a two tier billing system for water. As a user you are billed for the water that you consume or use and then you are billed for the water that you discharge into the sewer system after it has been used. Most municipalities work on the assumption that 75% of the water used by a household is discharged into the sewer system.

How much water can be harvested off a roof

During a rainstorm many people wonder how much water came pouring off the roof that could have been harvested for use.

The calculation is relatively simple. All you need to know is the surface area of your house in square meters - not the roof’s surface area but the floor surface area. Generally it would be expressed in square meters.  Secondly you need a rainwater meter to tell you how much rain fell during a particular rainstorm. Generally is expressed in milliliters of rain.

Rainfall over Southern Africa

The rainfall  map indicates the average rainfall in South Africa. In order to design a rainwater harvesting system it is critical that you look at the average rainfall in the area that you want to install the system. The rainfall will determine the design and size of the system.  Major benefits can be derived from rainwater harvesting in the areas with the high rainfall.

Rainwater harvesting savings calculator

We get many questions about how much money will people will save with a rainwater harvesting system. We have built a calculator specific using the Durban Average mean rainfall per month to show interested people how much money a system can potentially save. Key to a rainwater harvesting system is that the water must be used on a continuous basis to achieve the required savings. 

A rainwater harvesting system must also be viewed as an asset to a building - so not only does it deliver a saving every month it adds value to the property.

Simply input the potential roof recovery surface and the property's monthly water consumption and the google sheet will calculate the savings.

You will notice a few things. 

  1. The bigger the recovery surface the greater the potential savings
  2. The more water the property uses the bigger the potential saving 
  3. During the winter months the property will use more municipal water - so the greatest savings are in the wet summer months

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