Various types of plastic materials are used in plastic piping systems. These materials display a wide range of properties that make pipe systems the ideal choice for anything from pressurised water mains to gravity sewer systems and indoor heating.
Polyvinyl Chloride or PVC is a thermoplastic material derived from common salt and fossil fuels. The pipe material has the longest track record of all plastic materials. The first PVC pipes were made in the 1930’s. During the 1950’s, they were used to replace corroded metal pipes and thus bring fresh drinking water to a growing urban population.
Soon followed further pressure and non-pressure applications in the field of sewers, soil and waste, gas (low pressure) and cable protection. The material’s contribution to public health, hygiene and well-being has therefore been significant.
Based on the standard PVC material, other variants are in use. A high-performance variant called CPVC is used specifically for indoor applications in hot water supply. Another variant called PVC-O represents an important landmark in the history of plastic pipe technology. This molecular structure is created by a bi-axial stretching of the material during the extrusion process which gives the pipes a very high strength combined with extra impact resistance.
In several studies the long track record of PVC pipes has been investigated. Investigations have confirmed that PVC water pressure pipes, when installed correctly have a useful life span of over 100 years.
Polyethylene or PE is a tough thermoplastic material. PE piping is used for a broad range of pressure applications including the transportation of drinking water and natural gas, irrigation, sewers and drainage lines.
PE has been used for pipes since the early 1950’s. PE pipe is made by extrusion in a variety of size dimensions. It is lightweight, flexible and easy to weld. Its smooth interior finish ensures excellent flow characteristics. Continuous development of the material has therefore enhanced its performance leading to rapidly increasing usage by major water and gas utility companies throughout the world. The weldability allows to either butt-weld or electrofuse weld the pipes to long lengths and thereby secure robust joints.
The pipes are also used in lining and trench-less technologies, the so-called no-dig applications where the pipes are installed without digging trenches and disrupt the activities above ground. Here the pipes may be used to line old pipe systems to stop leakage and improve water quality. These ingenious solutions are therefore helping engineers to rehabilitate pipe systems made of traditional materials. Excavation is minimal and the process is carried out quickly below ground.
The later years the PE materials have been developed with new properties. One example is PE-RC which has an extra high resistance against crack propagation and is therefore suited for no-dig installations with a potential risk of scratching the pipes when pulling it through the ground or through an old and leaking cast iron pipe. Furthermore, the PE-RC material allows the use of existing backfill material instead of sand when pipes are installed in the ground.
Also for PE pipe material, several studies demonstrated the long track record with expected lifetime of more than 100 years.
PP is a thermoplastic polymer made from polypropylene. It was first invented in the 1950’s and has been used for pipes since the 1970’s. Due to the high impact resistance combined with good stiffness and excellent chemical resistance this material is very suitable for sewer applications. Great performance at operating temperature range up to 60°C makes this material also suitable for in-house discharge systems in soil & waste application.
A special PP grade called PP-R is a copolymer for high temperature applications which allows it to be used for in-house hot water supply and many other industrial piping applications.
Cross-linked polyethylene is commonly referred to as PEX. It is a thermoplastic material that can be made in different ways depending on how the cross-linking of the polymer chains is done. The different cross linking methods are often expressed in different letters, eg. PEX-A, PEX-B, PEX-C and PEX-E.
PEX has been used for pipes in Europe since the early 1970’s and has been gaining rapid popularity over the last few decades. Often supplied in coils, it is very flexible and can therefore be led around structures without fittings. Its strength at temperatures ranging from below freezing up to almost boiling makes it an ideal pipe material for hot and cold water installations, radiator connections, under-floor heating, de-icing and ceiling cooling applications.
When used for heating applications the pipes are covered with a barrier layer to avoid penetration of oxygen through the pipe wall. PEX and also PE-RT can be combined with a thin aluminum middle layer. The aluminum serves two purposes: As an oxygen barrier and to increase the longitudinal stiffness of the pipe.
A thermoplastic polymer made from butylene. Polybutylene was invented during the 1950’s and widely used since the 1980’s. PB combines strength at high temperatures with a very high flexibility which makes installation easy. PB has found good use in hot and cold water installation.
Polyethylene of Raised Temperature Resistance or PE-RT expands the traditional properties of polyethylene. Enhanced strength at high temperatures are thus made possible through special molecular design and manufacturing process control. Its resistance to low or high temperatures makes PE-RT ideal for a broad range of hot and cold water pipe applications.
Acrylonitrile-Butadiene-Styrene (ABS) is a thermoplastic material which was originally developed in the early 1950’s for use in oil fields and the chemical industry. Today the material is also used to manufacture the famous LEGO-bricks. The variability of the material and its relative cost effectiveness has made it a very popular engineering plastic. It can be tailored to a range of applications by modifying the ratio of the individual chemical components. They are therefore used mainly in industrial applications where high impact strength and rigidity are essential.