Filters are the key component in rainwater harvesting systems that remove the majority of contaminants, from twigs and leaves right down to microscopic debris. Which filter type to choose depends on the volume of water being collected, with large commercial systems requiring more complex devices than relatively simpler domestic systems.
Traditionally, the simplest of all was some netting stretched across the mouth of a water butt beneath the drainpipe. This was not ideal as it would rapidly become clogged.
Today’s technology sees self-cleaning Vortex style filters that require little emptying or maintenance and work ceaselessly to ensure that storage tanks are free from debris.
What Are The Main Filter Applications?
Rainwater filters are designed for either one of the two primary purposes in a rainwater harvesting system:
- Pre-tank treatment, which remove as many physical contaminants as possible before the water enters the storage system
- In-tank filtration is a variation on pre-tank systems that see the filter deployed inside the storage tank but with the same effect as external pre-tank filters
- Post-tank filtration involves additional particulate filtering after the water leaves the storage system and is piped to application points, such as drinking water outlets
Pre-Tank Filter Types
The most important function of these filters is to prevent debris from entering the tank, so the finer the filter mesh the better (within reason). This helps to maintain peak quality and inhibit the development of anaerobic bacteria, which can lead to unpleasant odours.
- Downpipe filter – These are designed to extract the water and divert it to the storage system while leaving debris to continue down the pipe. The vast majority of water that passes through these downpipe filters is harvested – around 95% – thus minimising water loss.
- Vortex filter – A clever design causes the water to swirl around and against a mesh that prevents any particle bigger than 0.28 mm to pass through into the storage tanks.
One important additional functions of these Vortex filters is to oxygenate the water as it is filtered. Watch the video that explains the vortex filter technology and the action.
- Horizontal filter – specifically designed for commercial sites where a low invert loss is required (difference in height between the inlet and outlet pipes), this style of filter utilises a mesh underneath the water flow to remove and wash away debris. See the specification and explanatory video.
The LineAr horizontal in-tank water filter is a unique design that using the same technology as the Vortex filter within a horizontal unit within minimal invert loss, that is extremely efficient at removing debris. A useful animation explains the operation of the LineAr filter.
- Particulate filters – These are called particulate filters because the earlier filters are expected to have already removed physical debris greater than a certain size. Particulate filters are especially important when water quality needs to be raised from non-potable to a higher quality using an ultra violet disinfection unit. UV light neutralises the health risk from microbial sources and pathogens by destroying their DNA. The process requires that the water contain no particles that might throw shadows and prevent the UV light from reaching all areas, Hence the need for an inline particulate filter before the UV chamber.
- Carbon filters – these are used to improve the taste and odour of water.
When considering a rainwater harvesting and distribution system for your next project, it pays to obtain advice from professionals in the industry. We at Rainharvesting Systems are the UK’s longest established systems vendor and we are happy to draw on our wealth of experience to assist you in designing the most appropriate system to maximise a client’s investment. Contact us today for a free and no-obligation initial consultation.