Inlet boxes and connections

Channel elements with integrated inlet boxes are used as a transition to the existing sewer system. Inlet boxes usually have removable covers/grates and contain a sediment trap. In this respect, they function similarly to a street drain (gully). Currently, there is no specific standard for channel inlet boxes, but their design should meet the requirements for yard and street drains (formerly DIN 1236, 4052, now EN 124). In practice, inlet boxes are supplied by the channel manufacturer to match the system, tailored to the channel width and load class. The installation height can vary depending on the channel system and local conditions. Inlet boxes are available in one-piece, two-piece (upper and lower sections), or three-piece (with an intermediate element for height adjustment) versions. The inlet box is connected to the sewer system via lateral pipe connections on the lower section. Connections starting at DN 100 are standard. Many boxes have pre-drilled openings or break-off points that can be drilled out to the required diameter (e.g., DN 100, 150, or 200). If the volume of water to be discharged is small and the connection short, a box can sometimes be omitted entirely, and the main drain line can be connected directly to the gutter. For this purpose, manufacturers offer so-called direct outlet spigots, some with integrated debris traps and odor traps. For larger volumes of water, however, an inlet box with a storage chamber (for better sedimentation) is recommended. For very large flow rates, there are catch basins that are wider and more voluminous than standard inlet boxes. They can receive gutter inlets from all four sides and therefore have correspondingly larger sediment trap volumes. Catch basins are used, for example, at low points in large areas or when longer gutter runs converge.

The connection between the inlet box (or channel body) and the underground pipe is made using pipe stubs. These are short pipe sections, usually made of plastic (PVC or PE), which are inserted into the designated opening and sealed. According to the former DIN 19543 standard, these stubs had to meet the requirements for pipe connections (tightness, durability). Modern systems use push-fit sockets with sealing rings. It is important that the stub fits securely and is watertight, as it can be subject to movement (settlement, temperature fluctuations). For changes in direction in the channel line (corners, T-junctions, crosses), manufacturers often offer special fittings or pre-designed openings, allowing two or more channel runs to be connected at a corner. This enables, for example, drainage channels to be routed around building corners or several runs to be combined into a single drain.

End caps serve to terminate individual channel sections. These components are made of the same material as the channel (concrete, plastic, etc.) and are inserted into the groove. End caps are available with and without a drain outlet. If the run ends without a connection, a closed end cap is used. If a horizontal outlet is planned at the end of the run (e.g., to the sewer), an end cap with an integrated pipe connection can be selected. In high-stress areas, end caps with edge protection are also available to prevent chipping.

Channel systems are often complemented by special accessories. These include, for example, transition pieces for stepped slopes (to elegantly bridge changes in the channel's height), adapters for changes in flow direction, or special elements for specific applications (e.g., drains with catch basins for sports field channels, flat collection units for parking deck channels, etc.). Compatibility is crucial for all these accessories: Typically, a single manufacturer supplies the complete system, ensuring a precise fit and consistent material quality. The tender specifications should list which accessories are to be included (end caps, spigots, seals, etc.) to guarantee the system's functionality.