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Introduction
The materials used for constructing for the transportation of water have evolved over a very long period of time from the most basic ditches and stone channels in the years BC through hollowed out wooden logs to labour intensively constructed large scale brick sewers in Victorian times to the most modern of composite and manmade materials we see today.
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This page shows some of the more common materials seen today by CCTV surveyors during pipe inspections.
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Material Classes
Drainage materials are generally classed into two types, with two additional sub types:
Modular - sewer conduits that are constructed from small building blocks without any discrete joints, like brick sewers.
Piped - sewers and drains that are constructed from discrete jointed manufactured pipes:
Rigid pipes - pipes that have no capacity to bend when stressed under load, they just break.
Flexible Pipes - pipes that can absorb a degree of deformation without any loss of structural integrity as a result of their design and manufacturing process.
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Modular Sewer Construction
Modular sewers, usually referred to as ‘Brick’ or ‘Masonry’ are constructed using building blocks and mortar and are always rigid, but there is a distinct difference between the materials ‘Brick’ and ‘Masonry’ although the construction methods are basically the same:
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Where there is no option in a material list for tiled constructions, we would use ‘Other’ with a comment. Here, the sewer is constructed from manufactured interlocking clay tile segments creating a smooth internal surface that is hard wearing. If you look in the distance, you can see the design of the tiles where the sewer has failed and there were often two layers of interlocking tile skins in the construction.
Piped Sewer Construction
As written previously, piped sewers are usually sub divided into rigid and flexible groups where there are advantages and disadvantages of both:
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Lack of flexibility, so any local ground movement cannot be absorbed by the pipe joint, and the pipe simply breaks and cracks either side of the joint which in itself is a large immovable object under the ground.
Disintegration and loss of seal - when these pipes were laid maybe 100 years ago, society did not have the cleaning products that we have nowadays, most of which are advertised on our TVs as being able to effortlessly remove limescale from our kitchen worktops and bathroom basins. This feature of these products, which we just tip away down the plughole also dissolve away the lime in the mortar joints in the sewers, leading to joint failures and leakage both in and out of the sewer.
Flexible and Rigid Pipes
As mentioned, pipes can be sub divided into flexible and rigid materials. Generally speaking, it is easier to define which pipes are flexible materials, and therefor by deduction, if it is not flexible, it must be rigid.
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As far as the metals are concerned, there are two distinct properties of metals that come into play here - is the material malleable or brittle? These are terms used to describe the properties of the material, and materials like steel are malleable, which means that they will bend under load, even if it is very hard to actually do it, so it is a flexible material. On the other hand, cast iron is rigid. It does not bend, it just breaks, in the same way that concrete and clay do, but again, it is extremely difficult to actually do this in real life.
Clay Pipes
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