There are three main types of rainwater harvesting system: direct pumped, indirect pumped, and indirect gravity. In certain situations it may be possible to have a purely gravity system; though such occasions are rare.
The most basic form of harvesting is the humble garden water butt. Water collects in the container from drain pipes and/or natural rainfall, and is mainly used for the watering of garden plants. Users with gardens of a decent size will see a reduction in the amount of mains water used. Pairing the water tank with a rainwater filter can further improve the quality of the harvested rainwater.
This is the most common type of more professional rainwater harvesting system, particularly for domestic properties, and is generally the easiest to install. The pump is located within the underground tank and harvested water is simply pumped directly to the WCs or other appliances. If the tank should be in danger of running dry, a small amount of mains water is fed to it in order to maintain supply. For commercial projects, such systems tend to be dual pump arrangements (dutystandby).
This system differs in that the pump is not inside the tank, but instead is located within a control unit within the house (e.g. utility room). The unit also deals with the backup from mains water supply, so there is no need to send mains water down to the tank.
This type of system differs in that the harvested water is first pumped to a high level tank (header tank), then allowed to supply the outlets by gravity alone. With this arrangement, the pump only has to work when the header tank needs filling. Also the mains water is fed directly to the header tank, not into the main harvesting tank.
This arrangement is similar to the above, except that the internal tank can be at any level in the building, as it does not rely on gravity to supply the outlets. Instead a booster pump set is used to provide a pressurised supply. This system employs the benefit of not having to feed mains back-up water to the underground tank, whilst also offering great flexibility as the booster pumps can be tailored to suit the flow and pressure requirements of the building.
In some situations It may be possible to have a system that functions purely through gravity, requiring no pump and therefore no energy use. With this arrangement, rainwater is collected from a part of the roof which has gutters above the filter and collection tank which are in turn above all the outlets. This arrangement is ONLY ever possible where the storage tank can be located below the level of the gutters, yet higher that the outlets that it will supply. Only the power of gravity is needed to feed collected and filtered water to various parts of the home for use, so it is an ultra-energy efficient option.
Is Rainwater Treated?
Our rainwater harvesting systems filter water before it enters the storage tank. Debris such as moss, twigs and leaves are separated from the water before it enters the tank through a calmed inlet. Another filter, which is part of the pump assembly, rids the water of small particles before it is pumped to serviced appliances. The water harvested with these systems meets requirements for non-potable use.
Which System Is Best For Me?
Much depends on the individual situation. Where internal space is limited, or where it is not possible to fit a header tank, then the direct pumped systems are the best, particularly for domestic properties. Where it is possible to use a high level header tank, then the indirect gravity option can be preferable, especially where there is no requirement for the system to supply at high pressure. In large buildings or where high pressure is desired, then the indirect pumped system is the most appropriate.