GRAF Infiltration Tunnel/Tunnel twin

The GRAF Infiltration Tunnel has been mainly designed for the use in private and rural areas. The system which consists of one or several tunnel modules and two end plates can be extended at will. The laying is realized in one or more lines of the same level. As the weight of one module is only 11 kilos, the handling of the Infiltration Tunnel is excellent.

The surface beyond the tunnels is vehicle loading which offers versatile possibilities for utilisation.

Thanks to its special design the GRAF Infiltration Tunnel can be stacked easily. Consequently, the shipment of up to 40 Infiltration Tunnels on one pallet saves considerable transport and storage costs.

Easy installation

The GRAF Infiltration Tunnels are laid in lines and can be flexibly adapted to specific conditions and to the individual storage volume requested. The installation of the modules is easy, quick and variable. The installation is possible without heavy equipment, as one Infiltration Tunnel only weighs 11 kilos.

The tunnel modules are simply stuck together in one line and equipped with 2 end plates per line.

Best ratio storage volume/weight

  • Polypropylene materials
  • Dimensions 1.20 x 0.80 x 0.51 tunnel, 1.20 x 0.80 x 1.02 twin
  • ratio 100%
  • Best logistic characteristic – stackable up to 40 tunnels per pallet
  • Connection surface DN 100, 150, 200, 300
  • Link between two tunnels without equipment
  • Link between two twin modules with click-bolt system
  • Resistance to vehicle loading
  • earth covering between 250 to 1990 mm (Tunnel) and 250 to 1480 mm (Twin Tunnel)




Polystorm modular cell system, attenuation and soakaway solutions

The Polystorm principles

The Polystorm range of modular cell systems are designed with a 95% void ratio to retain large volumes of water run-off. The Polystorm cells can be designed and built to a specific size to a total void volume requirement dependent upon the water run-off volumes required on a particular project (i.e. car park, road or building). The Polystorm range of water storage cells are structurally strong, individual modular cells which can be built up to form a structure of any shape or size. The structure is wrapped in a non permeable, geomembrane which can receive rainwater collected from the roof gutter system or surface drains and either releases the water within set discharge limits (attenuation) or, where soil conditions allow, be wrapped in a permeable geotextile and slowly release the water back into the surrounding soil (soakaway).

There are three different types of Polystorm cells which are Polystorm Lite, Polystorm and Polystorm Xtra. Each Polystorm cell type has a different surface load specification.

  • Polystorm Lite is designed for use in landscaped pedestrian or other non-loaded applications
  • Polystorm is designed for use in light trafficked and loaded applications
  • Polystorm Xtra is designed for use in deeper build depths for heavily trafficked and heavy loaded applications


Key benefits

  • 95% void ratio: Providing greater water storage capacity and reduced excavation and disposal costs
  • Modular units: Allow flexibility of shape - ideal for shallow excavation systems, narrow strips or use in restricted areas
  • Light weight yet robust: Excellent Health and Safety and installation benefits
  • Easy to handle: Unique rounded corners for ease of handling and reduces likelihood of punctures to membranes
  • Cost effective: Especially when used as a hybrid, value engineered system
  • Recyclable: 100% recyclable at the end of its useful life
  • Range: Spans from 20 tonnes per square metre load bearing capacity up to a maximum of 80 tonnes per square metre load bearing capacity
  • The range can be designed for non-trafficked, trafficked or heavy trafficked applications
  • Suitable for both attenuation and soakaway systems
  • 50 year design life
  • BBA Approved
  • Hybrid Solutions


Brochures for Stormwater systems are available on request. 

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