Question 1

What is a channel drain?

Accepted Answer

A channel drain (or linear drain) is a prefabricated drainage channel installed at or below paving level to collect surface water from hard paved areas and convey it to an outlet at one or both ends, connected to the surface water drainage system. Unlike traditional point drains (gulleys and gratings at discrete points), a channel drain runs in a continuous line - typically at the lowest point of a paved area, at the junction between the driveway and the house, or across a slope to intercept overland flow. The channel body is set in concrete and the removable grate sits flush with or slightly below the surrounding paving surface. The internal fall is provided either by the channel units themselves (pre-formed with an internal gradient) or by the fall of the installation.

Question 2

What load class channel drain do I need for a driveway?

Accepted Answer

Channel drains are classified by their maximum load capacity to BS EN 1433: Class A15 (15 kN) - pedestrian and bicycle areas only, not suitable for vehicles; Class B125 (125 kN) - areas accessed by light vehicles (private cars); Class C250 (250 kN) - larger cars, SUVs, and occasional medium commercial vehicles; Class D400 (400 kN) - public roads and areas with regular heavy vehicle access; Class E600 and F900 - heavy industrial and aircraft apron use. For a standard residential driveway with car access only, Class B125 or C250 is appropriate. If the driveway is accessed by delivery lorries, waste collection vehicles, or similar heavy vehicles, Class D400 should be specified. Using an undersized channel that is overloaded will cause grate or channel body failure.

Question 3

How is a channel drain installed?

Accepted Answer

Channel drain installation requires: excavating the trench to the channel depth plus 100-150mm for a concrete surround; laying a level concrete base at the correct depth; placing the channel units on the concrete base, connected end-to-end with the outlet at the downstream end; haunching (surrounding) the channel body with concrete to prevent movement; and completing the adjacent paving to the correct level so the grate sits flush or 3-5mm below the paving surface to direct water in. The concrete surround must extend at least 150mm either side of the channel body and be brought up to within 25mm of the final surface level. The outlet from the channel connects to a surface water drain or soakaway via a standard drain connection. The channel must have a fall toward the outlet - minimum 1:200 for self-cleansing.

Question 4

Where should a channel drain be positioned on a driveway?

Accepted Answer

The ideal position for a channel drain on a driveway is at or near the boundary between the driveway and the public footway or road, positioned to intercept all run-off from the driveway before it can flow onto the public highway. This is particularly important for driveways on impermeable surfaces (tarmac, concrete, block paving) where planning policy in England requires that surface water from front driveways does not discharge onto the highway. A secondary channel position is at the junction between the driveway and the building, to intercept water and prevent it pooling against the house wall. For sloped driveways, the channel should be sited at the bottom of the slope to catch the maximum run-off flow. On permeable driveways (resin-bound, permeable block paving), a channel drain at the boundary may still be needed to handle peak rainfall events that exceed the infiltration capacity of the surface.

Channel Drain

Just so you know...