Types of rainwater harvesting systems

Introduction



The term rainwater harvesting is used to mean the collection of roof water (typically) from a building to provide that building with water to displace mains water. Rainwater in its untreated form can be used instead of mainswater (potable). This means that you can use rainwater (non-potable) in WC's, washing machines and all outside tap functions. Our studies have shown that this accounts for approximately 50% of all water used. So from an environmental perspective, we reduce our mains water consumption by 50%. (subject to the amount collectable from the roof). In commercial projects the amount could be much higher. As the vast majority of water used in an office is for WC's.

Rainwater harvesting systems are have a essentially three main components, these being:

• Storage tanks


• Filters


• Control systems

But there are of course variations on the above.

1. Storage tanks, these can be underground, above ground single peice, above ground sectional. Made from GRP, concrete, plastic or metal.


2. Filters, course leaf and grit, self-cleaning, backwash and inline strainers.


3. Controls can either be direct pump pressure, header tank (gravity) with or without mains top-up. They have a single pump or multiple pumps. These pump can either be submersible (in the tank) or suction pumps (sited with the control panels).
   

In addition to the main components, all items are sometimes added such as ultra-violet sterilisation or monitoring panels as shown above. These add-ons are not required in order for a system to function, but they make the systems more pleasant work with.

When using a rainwater harvesting system it is important to ensure that it complies with the water regulations (WRAS). This is mainly concerned with the cross-contamination of potable and non-potable water and also correct pipe markings inside and outside the building.