The length, width, and height of the retention tank can be adapted to the local infrastructure.

Everything from the one source: Planning, supply, and installation on site

The retention tank setup provides the option of adapting the length, width, and height of the welded storage crates to the local infrastructure. The advantages of using storage crates come into play especially when the specified building window do not permit conventional tank installations. As early as the planning phase and right up to installation, GRAF provides assistance in the setup of a retention system with EcoBloc Inspect storage crates.

Rainwater retention with EcoBloc Inspect:

Setup as a Tank

Retention capacities can be realised with both moulded tanks and storage crates welded into in a waterproof plastic liner. In the expanded version the storage crates have a non-woven 300g sheet of geotextile (or similar) laid over the top of the tanks. They are then wrapped completely in a 1mm LLDPE plastic liner, and then finally in a non-woven 300g geotextile.

**This setup is referred to as a complete tank. The surface layer of geotextile protects the waterproof plastic liner (tip: LLDPE plastic liner, 1mm thick) from sharp block edges, while the outer layer of geotextile prevents damage from the surrounding earth or stones.**

Setup as a Tray

A simpler variant of a tank setup with storage crates is based on the tray principle with an open cover. Here, the sides of the waterproof plastic liner are extended upwards, and are not sealed with an additional “cover”. This reduces the additional welding work in on the top of the tank, however the tank is only watertight to the top edge of the storage crates. The uncovered areas allow water to flow in and out of the tank. In specific cases, this may be desirable or be seen as the ideal project solution.

Flexible Solutions

The advantages of designing a retention system with storage crates are their flexibility to adapt to different tank sizes and loading classes in the building window. Larger retention systems can therefore be achieved, which is not the case with conventional retention tanks.


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