What is an ACO drain?

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.

What loading class do I need for my ACO 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.

How should an ACO drain be bedded?

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.

How many outlet points do I need?

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.

Do I need a sump unit?

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.

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

Calculate ACO-style channel drain components including channel lengths, end caps, corners, outlets, gratings and sump units to BS EN 1433.

Total Run Length

Total linear length of channel drain

Number of Corners

90-degree corners in the drain run

Number of Outlets

1 outlet per 10-15m of run

Grating Type

A15 — pedestrian and cycle only

Price Per Metre (optional)

Price per metre of channel for cost estimate

How We Calculate This

This calculator determines the components needed for a linear channel drainage system based on your total run length, corner and outlet requirements.

The formula

Channel lengths = ceil(Total run length / 1m)

Standard ACO-style channel drain units are 1 metre long. The total run length is divided by 1m and rounded up to determine the number of channel units needed.

Components calculated

Channel lengths (1m): The main channel body units
End caps: 2 per system (one at each dead end)
Corner units: Special units for 90-degree bends
Outlet units: Connect the channel to underground drainage
Sump units: Debris/silt collection at each outlet
Gratings: One per channel length plus one per corner unit

Standards

Channel drainage systems must comply with BS EN 1433 (Drainage channels for vehicular and pedestrian areas) which defines loading classes from A15 to F900. The installation should also comply with Part H of the Building Regulations for connection to the drainage system.

Frequently Asked Questions

Last updated: February 2026

All calculations are estimates. Verify with your supplier.

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

How We Calculate This

The formula

Components calculated

Standards

Frequently Asked Questions

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