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  • Rainwater Harvesting Filter Kit for roof areas up to 800m2.
  • How the Rainwater Harvesting Twin Filter works.
  • An example of the Twin Filter wall mounted on an agricultural building in a frost free position.
  • Example Rainwater Harvesting System showing the four Filtering Steps in a professional Rainwater Harvesting System, keeps the collected water in the best condition in the water storage tank. Note the filter in the image is NOT the Twin Filter.

Rainwater Harvesting Filter Kit for Roofs up to 800m2


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Product Description

With good planning and the right components, a rainwater harvesting system can be nearly maintenance free and the rainwater quality ideal for many uses both in the home, workplace or in industry. A good professional system will have four steps of rainwater cleaning. To make it easier for you to harvest rain using larger tanks, often above ground tanks, we have created a range of Rainwater Harvesting Filter Kits. The Kits give you substantial savings over the components purchased individually.

This Rainwater Harvesting Filter Kit is suitable for new and existing water storage tanks including PE, GRP and concrete tanks (like for example Enduramaxx, Rototek, Wydale and Balmoral) where the collecting roof area is no larger than 800m2.

The Water Tank Filter Kit cover the first three steps of the professional rainwater cleaning system; filter, calm, overflow (the 4th step is the Floating Intake and included in our Rainwater Pump Kits). The Kit include an appropriate filter (sized according to the roof area), a calmed inlet and overflow siphon. They can be retro fitted into existing tanks, or purchased with new above and below ground rainwater tanks.

Rainwater Harvesting Filter Kit Components

STEP 1 - FILTER - Twin Filter

The first step in the rainwater system is the filter. The rainwater flows from the roof to the filter. Here, dirt particles and debris are separated from the water. The cleaned water flows to the tank. The dirt is washed to waste or soakaway with a small amount of rainwater. All 3P Technik’s rainwater filters have stainless steel inserts, which are easy to remove and easy to clean. Their many different working principles and connection possibilities allow for their use in many different installation situations. Complies with BS8515.

This Rainwater Harvesting Systems come with a filter sized according to the maximum roof area you will be harvesting from.

The Twin Filter filters rainwater from roof areas up to 800m2 and is perfect for installation before rainwater tanks as part of a large rainwater harvesting filter system. Install either directly to a wall in a frost free location using the wall brackets supplied, or in an underground chamber (1000mm diameter).  Height difference between the rainwater inlet and outlet of just 510mm.


In the rainwater collection tank, any residual particles heavier than water settle to the bottom of the tank. The 3P Technik Calmed Inlet ensures that oxygenated water is introduced to the lower layers of the stored water in the tank without disturbing the settled sedimentation. This oxygen-rich water prevents anaerobic reducing conditions forming in the storage tank and ensures that the water stays fresh.

The Calmed inlet sits on the bottom of your rainwater tank and is connected to the filter using a length of standard DN100 pipe (not supplied).


Particles lighter than water (e.g. pollen) float slowly to the water surface. 3P Technik’s expertly designed overflow siphons, with a skimmer effect, removes this floating layer. The regular overflow from the storage tank is vital to obtain optimum water quality. It prevents souring of the water. The floating layer will otherwise build up over time, and so reduce oxygen diffusion at the water surface, which in turn could lead to anaerobic reducing conditions in the tank.

We have chosen 3P Technik's Uno Overflow Siphon for this kit. It skims the surface water of debris and the U-bend design ensures any smell escaping from the tank and deters rodents and other animal life getting into the tank.

All 3P components are BS8515 compliant.

Optional Extras

Rapid Connector Sets (110mm)

110mm pipe connector complete with steel nuts, bolts, washers & seal insert. These Double Socket Slip Couplers can be used instead of a Double Ended Coupler. The Rapid Connectors ensure that you don't have to move the connecting waste/drainage pipes to fit or to undo the filter at a later date. They enable the pipe to be simply bolted to the filter while it is in place rather than pushing pipes into a socket coupler or similar. Note; the filter basket can be accessed, removed and cleaned by taking the lid off (if purchased) the filter housing - the entire filter housing doesn't need to be taken out for cleaning maintenance.

Technical Information

  • Installation on a frost free wall above the storage tank.
  • Stainless Steel filter cartridge mesh size: 0.65mm.
  • Filter according to DIN 1989-2, Type C, exceeds BS8515.
  • Height difference between rainwater inlet and outlet 510mm.
  • Also available without Wall Brackets (contact us for details).

For specific technical information about each of the components, please see their web page:

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