With a growing acceptance of their use as an alternative to concrete and in light of Sewers for Adoption 7 (SfA7), which allows engineers to specify plastic inspection chambers, it’s important for contractors to consider the benefits of modern plastic systems.
The SfA7 guidance provides installers with general specifications for drainage with the intention of standardising the performance and installation of all ‘adoptable’ drainage installations. Adoptable inspection chambers serve two or more properties and are the first inspection chamber back from an adoptable lateral drain.
A key requirement and a major change with SfA7 for specifiers is that tried-and-tested engineered plastic inspection chambers are now being accepted for use in adoptable areas and are unlocking significant cost and time benefits.
SfA7 incorporates Typical Access Chamber Details for flexible material (plastic) versions. This means that traditional rigid concrete chambers are no longer the only authorised option for adoptable drainage installations down to 3m.
Plastic inspection chambers are now required to comply fully with BS EN 13598 under SfA7 guidance. Part 1 of the standard covers installations down to a maximum of 1.2m invert depth and Part 2 covers deeper installations, including critical areas. Traditionally there has been some reluctance
towards plastic inspection chambers from water authorities, even for Part 1 compliant installations. This change, enshrined in SfA7, has begun to result in a change of attitude from the water companies.
One of the reasons why plastic systems are becoming more accepted is due to the rigorous testing program set out in BS EN 13598. Furthermore, a product certified by a third party (such as BSI) will be subject to this robust test program on an ongoing basis, ensuring that companies are consistently producing a product which meets this high standard. This impartial testing and certification should not only give water companies confidence in the system which they have installed, but also builders, surveyors and home-owners as well.
Modern plastic systems are seeing increased interest due to their important set of benefits compared with concrete, including performance characteristics such as structural integrity, watertight construction and strong loading capabilities.
Plastic sewer systems are also known for a very smooth internal surface. This reduced friction coefficient helps the flow of foul water, reduces the risk of blockages and means that the jetting pressure required for a plastic system is significantly reduced.
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