The focus on drainage couldn’t be more acute given the recent weather. Today’s high performance residential drainage systems ensure the effective removal of rainwater from vulnerable areas, preventing the ponding and accumulation of standing water that can cause damage. Nathan Baker, Product Training manager at drainage specialists ACO Technologies, gives advice on selecting and installing channel drainage systems that are specifically designed for residential applications.
Over the past five years, domestic channel drainage systems have become increasingly popular, replacing the point gully systems that were traditionally used on housing developments and on small/medium hardstanding areas. This has been down to their ease of use – none of the complex or multiple falls demanded by point gully systems are needed – their versatility, their performance and, ultimately, their high quality installed finish.
There are two categories of channel based on the material used in their manufacture – plastic and polymer concrete. It used to be that familiarity and tradition dictated which was preferred, but today (with the increasing sophistication of production methods, the introduction of new material compositions and the expanding arenas in which the channels are used) it is the application that is the basis for selection.
The common misconception is that plastic channels do not have the strength to withstand regular loading and are hence prone to failure. This is not the case - with improvements in material technologies the latest generation of plastic channels have the inherent strength to see them used in areas where heavier weight products were once the only option.
A good example of the enhanced performance that plastic channels now offer is ACO HexDrain®. This unique, lightweight system derives its superior strength and rigidity from HexTechnology™ - a patented moulding technique that surrounds and supports the channel with interlinked hollow hexagonal sections. These provide an exceptional strength to weight ratio – the channel weighs less than 2kg per metre and has a certified Load Class rating of A15.
Its performance is tailored specifically to pedestrian areas such as paths, patios and landscaped areas; driveways with occasional traffic and cycle paths. Combined with its three grating options – black plastic, metallic effect plastic and galvanised steel - the installed system provides an excellent aesthetic finish for even the most sensitive domestic setting.
Enhancements have also been made in the way the product is installed. Many plastic channels have a grating retention system, but these tend to cause problems when installed as any slight flex in the channel wall results in the grating being held too firmly for it to be removed when cleaning is required. The new HexDrain ‘friction-fit’ system gives a softer hold and completely eradicates this problem.
The problem of unsightly gaps appearing between installed grating sections has also been overcome with the introduction of a series of eight ‘anti-shunt’ pinnacles on the horizontal shelf that holds the grating. These mate with the underside of the grating and prevent any longitudinal movement once installed.
Polymer concrete channels are well established in the domestic environment – the toughness of the material being fully exploited to give exceptional strength, durability and chemical resistance. The latest designs have sought to further refine how they can be used, allowing installers greater flexibility.
ACO pioneered the development of polymer concrete systems with RainDrain. In its latest version - ACO RainDrain Plus® - the structure of the channel has been extensively re-designed so that it can be used for both Load Class A15 and B125 applications by simply selecting the appropriate grating.
The channel’s galvanised steel grating achieves a fully certified A15 rating, making it suitable for all pedestrian areas and driveways. But by switching to a new cast iron grating, the load performance increases to B125 – ideal for public pedestrian precincts, static vehicle loadings and private car parks.
By building in this flexibility it then becomes a much simpler task to alter the use of the surrounding land as none of the drainage infrastructure needs to be changed. This is a real benefit for areas that may need to be altered to accommodate higher vehicle loads as land is re-developed.
Avoiding the Pitfalls
Naturally, the full benefits of all these systems can only be realised if they are installed correctly. The fundamentals for both polymer concrete and plastic channels are the same:
1. Ground conditions:
To ensure that the long term ability of the channel to withstand vertical and lateral loads (pedestrian or vehicle) is sustained, the ground conditions, surrounding pavement and supporting concrete bedding must be stable. Every channel system is supplied with minimum installation dimensions – these should be checked for suitability against the specific ground and loading conditions of the site.
2. Laying out:
First, locate the exact position where the outlet/sump connection point from the new channel will be. Set out the network of straight channel runs from this point. Mark the finished channel grating height with a fixed line a minimum of 3mm below the finished surface level of the surrounding pavement.
3. Block Pavements:
If the channel is installed in a trafficked area, the blocks laid directly against the channel must be restrained from any movement by being bedded securely onto the channel’s concrete haunching. Blocks bedded on sand remote from the channel should be set at a higher level to compensate for any settlement.
4. Channel protection:
By ensuring that the channel is installed below the finished surface pavement level, the use of compaction equipment (if asphalt is used) will not damage the channel or grating. Covering the grating before concreting the haunch or laying asphalt avoids having to clean the finished channel of material and embedded stones.
Site traffic should never cross an unprotected channel before installation is complete. A temporary crossing can be formed by raising the asphalt base course 3-5mm above the grating level either side of the channel.
5. Movement Joints:
The channel must be isolated from lateral loads resulting from thermal of concrete slabs. A joint may be positioned up to 1.0/1.5m from the channel.
ACO Technologies runs full training courses on the design and installation of all its domestic and commercial drainage systems. For further information contact ACO Academy on 01462 816666 or via the website www.aco.co.uk