ACO Drain Calculator — How Many Channel Drain Lengths Do I Need?

ACO is a leading brand of linear channel drainage system. 'ACO drain' has become a generic term (like 'Hoover') for any linear channel drain. These are narrow channels set into the ground surface with removable gratings, used to collect surface water across driveways, patios, garage thresholds, and commercial premises. Other manufacturers include Birco, Hauraton, and Clark Drain.

The loading class depends on the traffic the drain will carry. Class A15 (1.5 tonne) is suitable for pedestrian and garden areas. Class B125 (12.5 tonne) is needed for domestic driveways and car parks where cars will drive over the drain. Class C250 (25 tonne) is for commercial areas with occasional HGV access. Class D400 (40 tonne) is for roads and areas with regular HGV traffic.

ACO channel drains should be set on a minimum 100mm concrete bed (C20/25 mix) with 100mm concrete haunching on each side. The grating level should be 3–5mm below the surrounding surface level to ensure water flows into the channel. The channel should have a minimum fall of 1:100 towards the outlet or sump unit. Use our Drainage Gradient Calculator to check falls.

As a general rule, provide one outlet for every 10-15 metres of channel run, or at the lowest point of the installation. For a driveway threshold, a single outlet at one end is usually sufficient. For longer runs, additional outlets prevent the channel from being overwhelmed during heavy rain. Each outlet needs a trapped gully or connection to the surface water drainage system.

Yes. A sump unit (also called a sand trap or silt bucket) should be installed at each outlet point. It sits below the channel invert and collects debris, leaves and sediment before they enter the underground drainage pipe. This prevents blockages downstream. Sump units have a removable bucket that should be cleaned out periodically.