The wisdom of rainwater harvesting


UK water market expert Aquaswitch writes

Businesses looking to reduce their environmental impact focus on reducing electricity and gas consumption, while water consumption is often overlooked.

There are two key reasons why water consumption should be targeted for reduction: the significant carbon footprint of water treatment, and the Environmental Agency’s stark warnings of water shortages, which are expected to arrive by 2050 based upon existing projections of consumption.

In Britain, there is no shortage of water falling from the sky. We explore why businesses should consider a rainwater harvesting system, the different types of systems available and the potential pitfalls of this water source.

How does rainwater harvesting work?
A rainwater harvesting system takes advantage of the frequent rainy weather to replace the need to use mains water.

Harvesting works by collecting and directing rainwater through an initial filter that removes twigs, leaves and other debris. After collection, water is pumped through to a second stage of filtration, called sedimentation, and then into a control unit used for the final filtration stage.

The filtered water is stored in a buffer tank until it is needed. Your mains water supply is used only to top-up additional water when there isn’t enough rainwater in the tank.

Before the water is used, it passes through a UV disinfection unit that kills bacteria. This is essential if the water is going to be used in an office environment.

The filtration processes in rainwater harvesting will ensure your business uses the cleanest water possible whilst reducing your overall water consumption.

Legionella risks to consider
Rainwater harvesting systems, by design, store water until it is required for use. This introduces a risk of Legionella growth that must be considered from a health and safety perspective.

However, you can reduce the risk of Legionella growth by:

  • Ensuring you include a UV disinfection to kill the Legionella bacteria
  • Flushing the harvesting system regularly by emptying the water from the storage tank. Install the water tank underground to reduce the temperature of the stored water.

Why should your business implement a rainwater harvesting system?
There are plenty of benefits to using rainwater harvesting, from reducing your impact on the environment to saving huge amounts on your water bill. Benefits include:

  • Reducing your overall water consumption as a business
  • Cost-effectiveness
  • Improving your overall impact on the environment
  • They are simple to implement and easy to use
  • Harvesting rainwater helps to secure a favourable BREEAM certification

The different types of rainwater harvesting solutions
There are a few different options, with tradeoffs to consider that will favour certain approaches over others, depending on your type of business.

The different types of rainwater harvesting systems are:

  • Water butt: Water is collected from natural rainfall, roof runoff and drainpipes. Usually only suitable for watering a garden.
  • Direct-pumped (submersible): Water is collected in an underground tank, and the harvested water is then pumped to the desired location.
  • Direct-pumped (suction): Difference from the submersible approach in that the pump is not inside the tank but within your premises control room.
  • Indirect gravity: This harvests rainwater initially pumped into a high-level tank, which is supplied to the individual outputs by gravity alone
  • Indirect pumped: Similar to the indirect (gravity) setup, except the internal tank can be at any level in the building as this setup does not rely on gravity to pump the water through the building.
  • Gravity only: This is a system that can rely entirely on gravity and requires no energy input. The arrangement of this system is explicitly designed to allow gravity to do all the work. It will only work if the storage tank is stored below the level of the gutters and other water collection systems.

How much water can be saved by rainwater harvesting?
Businesses have been able to reduce their overall water consumption by as much as 40% using a rainwater harvesting system.

It dramatically reduces your overall water costs and allows your business to operate in a more environmentally friendly manner.

If you want to learn more about rainwater harvesting, Aquaswitch has provided an in-depth guide.

We hope this information was useful to you; at AquaSwitch, we look to educate businesses on how to reduce their water consumption and how to become a water-efficient business, reducing both costs and the impact they have on the environment.