Rainwater harvesting refers to the collecting of rainwater, mostly on a roof, from where it flows through gutters into a collection tank. It refers to a storage system which could be either above or below the ground-that collects, stores and distributes run-off of rain or snow from roofs.

It reduces the use of treated municipal water for uses such as landscaping, toilet flushing and laundry. However, If your gutters are not clean, or there's a build-up of debris in them, that can cause disease in plants if you use the water on them, especially seedlings.

Some advantages of rain above ground harvesting:

• Easily accessible
• Set-up costs are low, with construction easy, materials low-cost and maintenance cheap
• Sustainability is higher.

Components of a rainwater harvesting system

A rainwater harvesting set-up is composed of a water-collection system, a storage cistern and a water distribution system. It mainly needs:

• Rain, and plenty of it preferably
• A catchment area
• Gutters or pipes
• Storage tank
• Filter (can be a simple metal screen filter or slow sand filter or even more sophisticated types if required or available)
• Pump or pressure tank for distribution

Underground Rainwater Harvesting

Underground systems can be used to feed water to almost any domestic property, and are most commonly used for supply the house with water for toilets, laundry and outside use, though are also often used solely for garden purposes. They can connected up to sprinklers and external taps, eliminating the need for the user to access mains water to maintain their garden. This brings cumulative cost savings for the property owner, especially in houses with large gardens.

The most obvious feature of an underground rainwater harvesting tank is that it is designed to be installed below ground level, rather than above ground either. This makes the system more advantageous for some purposes than others, as we shall see below. While every underground rain harvesting system will be unique to the individual property, all have certain features in common. These are:

Rainwater Collection System

Rainwater run-off is captured from the roof of a building from its’ drainage system. This can either by done directly from the rainwater downpipes (RWPs) or, more commonly from the below ground storm water drainage pipes. Leaf guards can also be used where many trees are present as this prevents an accumulation of decomposing leaves within the gutters. Where the tank is being fed by water from two different sources, e.g. from a house and an external garage, the pipes should all ideally combine in to one common pipe; this enables all of the water to be filter by a single filter collector.