The 150-litre tunnel is designed for infiltrating rainwater and treated wastewater into the ground. Rainwater is drained from the roof via pipes into the drainage tunnel, where it is freely infiltrated into the ground. The device can be sited in green areas (pedestrian traffic). When using drainage tunnels, it must be remembered that they can only be used in permeable and poorly permeable soils where the groundwater level is sufficiently low. The tunnel is made of polyethylene.