pro landscaper magazine
pro landscaper magazine

ACO Presents: Building Threshold Drainage Series

by | 19 Jan 23 | Promotion

When creating new gardens and patios or for landscaping over existing spaces, effective drainage must be front of mind. In the final chapter of this four-part series on threshold drainage, Rob Butcher, Design Services Manager at ACO Water Management looks at different ways to connect downpipes to drainage channels.

The threshold at the entryway or exit of any property is often a delicate balancing act of function and aesthetic. While an entirely level route from inside the home to the garden has become popular in recent years, the effect comes with inherent complications.

The raised patio necessary for a feature like this invites drainage problems that can cause damage to the building and make entering or leaving dangerous due to water ponding on the surface and being slippery. or those thinking of creating a raised-patio entryway, appropriate threshold drainage design is key, and one element of this is how downpipes are connected to drainage channels.

How to connect downpipes to drainage channels

Two techniques are commonly used to feed water from a downpipe into a channel drain. In order for water to reach the channel at ground level, one method is to have the downpipe positioned above the grating. Another method place is to connect the downpipe directly to the drain via the grating, so that rainwater can flow straight into the channel.

In either case, it’s crucial that the channel drain has the hydraulic capacity to cope with the volume of water coming from the roof and going down the roof’s downpipe. When it rains, water leaks out of the drainage channel and onto the patio if the hydraulic capacity is too low. This can result in damp and even flooding the inside with a threshold-level patio. Thankfully, it is simple to verify the hydraulic capacity required of drainage channels.

If you are unsure, you can use ACO’s QuAD design software, which has data on rainfall intensity by location, will help to better understand how much rain is expected to fall on the roof, and the channel capacity needed for the job. The software can also help with channel design and specification too with its product optimiser feature, allowing you to find the smallest and most suitable product for the project.

For more information on threshold drainage and the solutions available, visit

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