Rainwater Tank System: Useful Tips in Harvesting Rainwaters

Rainwater harvesting simply collects the rain which fall onto roofs, then stores it in a tank until required for use. When required, the water is then pumped to the point of use or to a secondary tank (header tank or break tank), thus displacing what would otherwise be a demand for mains-water. In the process, a volume of water is kept out of the storm-water management system, thereby helping to reduce flooding risks. Rainwater harvesting is not a new concept; however, over the last century its use has diminished with the availability of a clean, inexpensive and reliable water source through the mains supply.

More recently, water demand has started to exceed supply, and localised flooding has become an issue. Industry experts are now recognising the important role that rainwater harvesting (also known as rainwater recycling, and greywater recycling) has to play in alleviating both these problems. With strategic water planners looking to reduce the amount of water consumption per head going forward. Solutions such as rainwater harvesting will play a critical role. Rainwater is captured from the roof(s), and brought to a central point, via normal guttering and down-pipes, to enter a storage tank (frequently underground), where it is filtered on entry. A highly efficient and reliable submersible pump delivers the water to a service on demand. Depending on the circumstances a secondary tank (header tank) can be used to gravity feed the water to the point of use.

The size of the storage tank is determined by considering the amount of water available for storage (a function of roof size and local average rainfall), and the amount of water likely to be used (a function of buildings occupancy and function). It is very important not to over-size the rainwater tank too much. An over-sized tank may result in a lower than expected quality of water.
Considerations for fitting a rainwater collection system to an existing property

• The external drainage from the roof needs to be modified to bring the water to a central point.
• Access for the tank and excavation is required.
• Internal plumbing is usually required to be separated out from the drinking (incl. bathing) water from the non-drinking water (WC, washing machine & outside tap.)