Clean Tech 101

What is Rainwater Harvesting and the Importance of Harvesting Rainwater

Our most valuable natural resource is water. The rapidly expanding world population twinned with the effects of climate change are putting pressure on the world’s water resources. The UN has reported a direct link between poverty, hunger and water stress, making it a critical issue.

One example of water becoming a dwindling resource is the recent flash droughts in the US states of California, Montana and North Dakota where conditions have been the driest since records began. This has led to devastating wildfires and disruption to agriculture, energy production and manufacturing.

Utilizing the free supply of clean water that falls from the sky seems an obvious solution to this issue.

Water butt system

A water butt is rainwater harvesting in its simplest form where a tank is plumbed directly into roof guttering. Water butts have a capacity of around 200 liters and are typically used for outdoor applications such as gardening and car cleaning.

Domestic rain water harvesting systems

A more complex form of rainwater harvesting system is a three-step process involving the collection of rainwater from surfaces such as roofs, which is sent through a filtration/disinfection system and into a storage tank for later use. This type of system can provide in the region of 50,000-130,000 liters of water per year for a domestic system depending on rainfall levels and roof size.

Gravity-fed systems

A tank is mounted at the top of the building and uses gravity to distribute the water where needed. The obvious benefit of this type of system is no external power source is required, the water is collected from the roof and fed directly into the filter system of the tank and flows down with gravity to wherever required.

Pump-fed systems

The tank is mounted at ground level or underground, the latter is preferable as it saves space and allows the water to be cooled to prevent dangerous bacteria growth such as legionnaires. The water is distributed through a pump around the house.

Commercial Rainwater Harvesting

In the past 20 years, the average water bill in the UK for industrial premises has increased by 40% creating a strong economic argument for using rainwater harvesting. Furthermore, industrial premises often have large roof areas meaning large volumes of rain can be harnessed. Industrial machinery requiring water functions better with rainwater compared with ‘harder’ treated mains water.

The millennium dome in London uses a water collection system, taking advantage of its 900,000 m2 surface area. A Honda Dealership in Manchester has fitted a 30,000 liter tank utilizing a 1,500 m2 surface area providing a water supply of 85,000 liters a year and saving the company £1700 in water charges.

Rain Saucer

The Rain Saucer at a glance looks like an upside-down umbrella, however this simple innovation is a free-standing water collection system straight from sky to container. It offers simple potable water storage that can be transported and set-up in minutes, ready to go in the event of a disaster or in developing countries where clean water is either expensive or non-existent.

The video below shows the impact Rain Saucer has had in providing drinking water in Guatemala.

Image Credit:

Ajay Tvm/


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