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Rainwater harvesting

Conventional supplies of water are often costly, especially when water resources are
scarce. Reduced reliance on conventional water supply systems such as lakes, rivers, underground aquifers, bottled and desalinated water can provide bottom line business benefits in addition to benefits to the environment. Costs of implementation, construction, and maintenance for rainwater harvest systems are often recovered within a few years. Furthermore, the re-use of rainwater can improve the overall BREEAM performance for a building. BREEAM (BRE Environmental Assessment Method) is an environmental assessment for buildings (new and existing) developed by BRE (Building Research Establishment). 

Rainwater harvesting is different to grey water harvesting. Grey water harvesting is the use of waste water from sinks, baths, showers and domestic appliances for secondary use, such as flushing toilets. Rainwater harvesting yields much higher quality water and can be used for a wider range of applications.

Rainwater harvesting requires sufficient catchment area which is usually in the form of land surface or roof space. It also requires devices that will capture and store the water, such as rainwater barrel or underground storage tanks, and a conveyance system such as drain pipes and pumps. The water is usually passed through a filter prior to storage to remove leaves and other debris.

There are 3 main types of Rainwater harvesting systems 

  • non-pressurised: the rain water is held in a header tank and is gravity fed to the required area
  • pressurised: pumps are required to pump the water from a storage tank, often underground, to the required area
  • combination: this works on a combination system of the two above where pumped water is used to boost at times of high demand

The British Standard for rainwater harvesting BS8515 is a Code of Practice that covers the design, installation, checking water quality and required maintenance of rainwater harvesting systems. BS8515 also helps you to address design to ensure that there is no risk of cross-contamination between mains drinking water and rainwater.

Is Rainwater harvesting suitable for me? Further information can be found on the websites listed below:  

The UK Rainwater Harvesting Association
The Water Regulations Advisory Scheme 
Also the WRAP Information and Guidance Note No 9-02-04 Reclaimed Water Systems: Information About Installing, Modifying or Maintaining Reclaimed Water Systems

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