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Rainwater Harvesting Systems
Catchment Area
The catchment area is the first point of contact for rainfall. For most of the tank-based rainwater harvesting systems, the catchment area is the roof surface.
The size of the catchment area or roof will determine how much rainwater that you can harvest. The area is based on the “footprint” of the roof. The image left shows how differences in roof slope do not change this building’s catchment area.
The slope of the roof affects how quickly water will runoff during a rain event. A steep roof will shed runoff quickly and more easily clean the roof of contamination. A less-steep, flatter roof will cause the water to move more slowly, raising the potential for contamination to remain on the catchment surface.
Conveyance
The conveyance system is a fancy term for the gutters and downpipes. These are basically the networks of pipes that move the water from the roof surface to the storage containers. When selecting gutters and downpipes, it’s important to consider three factors: sizing, proper installation, and aesthetics.
Pre-storage treatment
The goal of pre-storage treatment is to clean the rainwater runoff as much as possible before it enters the storage tank.
Debris includes leaves, sticks, branches, or anything else that finds its way onto the roof surface. Debris can clog and damage RWH components and can add organic matter to the storage containers.
We use various methods that helps to reduce debris and organic matter from collecting in the tank.
Leaf catchers
It is important to install leaf catchers either at each downpipe or in the gutters being used for rainwater catchment. These screens remove debris that gathers on the catchment surface especially If a building is surrounded by many trees.
First flush system
These diverters should be installed on each downpipe that supplies water to the tank.
Storage
The storage container (cistern, is often the most visible or recognizable component of a RWH system. It is where the captured rainwater is diverted to and stored for later use. The main goal of the storage tank is safety. It should store water that is safe to use, and it should be secure so that children or animals cannot access the tank.
Plastic tanks are the most common material used for residential RWH systems in Texas. This is because they are lightweight, come in many sizes and colours, and can are affordable.
For a storage tank to maintain good quality water, it must not allow for any light penetration. Sunlight entering the tank causes algae growth.
The ground where a water tank is going to be located needs to be levelled and require either sand or concrete foundations.
Distribution
The distribution component of a RWH includes all of the piping, pumps, and other devices that move water from the storage to the point-of-use. If you are using a RWH system for drip irrigation by gravity flow, the distribution system may simply be a length of drip tubing. However, if you plan to use the water under pressure, there will be a few more key components such as a pump, level and pressure controller.