Demo model of WISY inline rainwater filter

Primary rainwater filtration is critical to keeping a rainwater tank clean and maintaining a good quality of water inside the tank.  A good primary rainwater filter must be able to screen out organic material at high volume flows, separate it from the fresh rainwater and direct it away from the rainwater tank while diverting the clean water to the tank. The bigger the surface area of rainwater recovery the bigger the volume flow of water and the more difficult the filtration becomes. Ideally the filter must require little maintenance be able to integrate into the deign of the structure.

Many people think rainwater harvesting is simply putting a pipe straight from the gutter or recovery surface into a tank. Initially it works well but very soon as a result of the high organic load does the quality of the water starts changing. First colour of the water starts changing, and after long period of no rain the water has a funny smell to it.  The sediment build-up inside the tank starts blocking the pump filters and strainers. If the water tank is drained you will find a thick black layer of de-composing organic material at the bottom of the tank. Cleaning the tank is a dirty job and requires somebody to enter the tank and physically remove all the organic material.

Primary rainwater filters come in many shapes and sizes and need to be selected for every specific application.

If you want to ensure that the rainwater tank remains clean and that you would never have to clean the tank you must install a very fine primary rainwater filter – like complex Vortex inline filters. These filters strain out any items bigger that 0.28mm to .44mm and they are guaranteed to keep your tanks clean and free of large debris. Minimizing organic material in the tank ensures that the water is not deprived of oxygen which keeps the water fresh for longer. 

Vortex filters have the added benefit that they act as a type of first flush system. For these filters to start working effectively they require the surface of the fine filter to become wet. This only happens after about 50-100 liters have passed through them - effectively flushing the first amount of dirty rain water off the recovery surface  to the storm-water drain. Thus these filters do not require any first flush systems.


If you use a well designed filter you will notice that the water in the tanks are always clear, taste fresh with no funny smells. 

If you just want a relative simple unit you can purchase a inline leaf filter. Depending on the volume flow of the water through the system the unite become bigger and can handle a large volume of water. The units are generally sized according to the roof surface that it can capture and filter water from.



Wisy AG have recently introduced a new rain-water filter aimed at the price conscious rain-harvesting consumer.The operating principal and design is based on the highly successful stainless steel inline rain-water filter that Wisy AG built their success on.

The filter is manufactured from UV resistant polypropylene plastic for the body and stainless steel for the filter element. The filter comes with a 10 year guarantee.
The filter is self cleaning and is virtually maintenance free. It exploits water's tendency to adhere to surfaces to drive the water through the filters vertical filter mesh. This operation is so effective that over 90% of the water flowing through the downpipe is captured. The remaining water is used to flush away the debris that collects on the household's roof. The filter can be used to filter rain-water from a surface as large as 200m2. The filter screen filters all particulates larger than 0.28mm from the rainwater, resulting in clear, odourless water.
The filter is very easy to install and requires only a section of the chosen downpipe to be cut out. The operation of the filter is such that a tank overflow does not necessarily have to be installed. The filter is simply fitted at the same height as the maximum fill level of the tank and connected to the tank by 50mm piping. This improves the aesthetics of the installation and means that water drainage at the tank site does not have to be considered in the design of the system.
The Wisy® RainCollector RS is the perfect solution for the urban rain-harvester who's looking to capture clean hassle free rain-water for gardening, laundry, toilet flushing and even drinking. See here if you want to buy one

See this Video1 and Video2 explaining how it works

RS110 rainwater filter installed

Wisy Downpipe filter


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