Des Dolan answers some of the misconceptions regarding the performance of plastic pipework systems

While plastic pipework systems are now readily accepted as a viable alternative to traditional metal materials, there are still many in the building services industry that are mistaken about the performance capabilities of plastic pipework products.

In its latest industry insight research, Durapipe worryingly uncovered that all of the contractors, consultants and end clients questioned had inaccurate information about the performance of plastic pipework systems.

One of the most common misconceptions is that all plastic pipework systems are the same and there is an assumption that the characteristics of one material will be the same with other plastic materials. However, every plastic material has different performance capabilities and has been specially designed for specific applications.

Myth: Plastics are more expensive

Fact: The mistake is often made of comparing initial material costs, but when looking at the installed costs of a system, plastics offer significant cost savings. The lightweight nature of plastic pipe systems, combined with their quick and simple jointing methods, significantly reduces the installation labour time and costs, offering installed cost savings of up to 50% compared with steel or copper systems.

Myth: Plastic pipes tend to snake due to thermal movement

Fact: While it is widely acknowledged that plastic materials expand and contract more when compared with metals, thermal expansion in plastic pipes can be easily catered for if addressed at the design stage of a project.

The simplest and most cost effective method of catering for thermal movement is to use the natural flexibility of the pipework system by building in changes of direction to the network design. The direction of pipe movement can be controlled by the use of anchor points at strategic positions. Other cost effective solutions include installing expansion loops, bellows, flexible hoses and expansion compensators.

Myth: Plastics are high maintenance

Fact: Plastic pipe systems require less maintenance than traditional materials, such as copper and steel. Corrosion is the biggest cause of maintenance and replacement costs in metal systems, with unseen corrosion in copper and steel HVAC systems having the potential to cause severe damage and significantly impact on operational efficiency. As a result, metal pipework systems need to be continually monitored, with regular flushing of the system scheduled, alongside taking frequent water samples to ensure the water quality is not adversely affected by any corrosion. With plastic pipework systems completely corrosion resistant this is not an issue, eradicating associated maintenance and repair time and costs.

In addition, the smooth bore of plastic pipe systems ensures no limescale can build up within the system, resulting in less friction loss and guaranteeing a consistent flow rate is maintained throughout the life of the system. With optimum flow levels maintained, minimal maintenance and repair work is required to ensure the system operates efficiently.

Myth: Plastic pipe systems aren’t designed to last

Fact: Plastic pipe systems have a 50-year design life, with the operational performance remaining at the same level throughout the lifetime of the system. The smooth bore of plastic pipe resists limescale build-up, ensuring flow is not restricted and continues at the same rate throughout its working life.

Myth: Plastics are more likely to encourage the growth of bacteria, such as Legionella

Fact: While copper has natural anti-microbial properties, as limescale builds on the used, corroded pipe surface, biofilm can begin to colonise more easily. Bacteria settle and develop in biofilm, which easily attaches itself to the sharp or jagged parts of a pipe's surface, which can be caused by the corrosion/scale build up inside a used pipe. A rougher surface will provide a stronger platform for biofilm to grow, due to the fact that rough surfaces have more surface area for bacterial attachment and growth and also provide more shielding from flow.

The smoothness of the pipe material is an important factor; while the surface of some metallic pipes is rough, the smooth bore of plastic pipes helps to limit biofilm development.

Myth: Plastics have low impact resistance

Fact: While not all plastic systems boast impact resistance, ABS is in fact an extremely tough material that provides very high impact resistance, with the pipe system remaining ductile even at temperatures as low as -40°c. Polypropylene is also a very robust material, remaining ductile down to -20°c.

Myth: Plastics are flammable and therefore a fire hazard in buildings

Fact: The plastics pipes industry has never claimed that plastic pipes are non-combustible. In a real situation, however, the use of exposed pipework within a room is unlikely and there has been no report, over the last 50 years, that the use of plastic pipes has contributed to any fire-related damage or injury, or increased risk to a property in the event of a fire.

In the UK, there are strict building regulations on the use of plastic, and all above ground drainage materials, which state that pipes should be installed within a duct or boxed in behind plasterboard. As a result, plastic pipework should always be concealed behind material of specified fire resistance, with furnishings and fittings much more likely to contribute to the spread of fire than any plastic pipes.

Myth: Plastic gives off large amounts of toxic gases when it burns

Fact: Some plastic materials can give off trace amounts, but not enough to be classed as hazardous in the event of a fire. As with many flammable materials, the primary hazard is smoke. All plastic products give off gases when the material is burning. The predominant gas with PVC-C, for example, is carbon dioxide, which is generally considered harmless.

Myth: Plastics are not sustainable

Fact: Plastic pipework systems offer strong sustainability credentials throughout all stages of their lifespan, requiring significantly less energy to manufacture, transport and install, compared with metal alternatives.

At every stage of its lifecycle, a plastic pipework system reduces the level of energy consumption, compared with metal pipe systems. On a typical commercial building project, the real impact of using plastic pipe and fittings equates to a 2,314kg CO2 saving, compared with copper, and a 3,606kg CO2 saving compared with carbon steel.

While one plastic pipework system may not be suitable for a specific application, it does not mean all plastics should be overlooked. Unlike metal systems' 'one product fits all' approach, each plastic pipework system has individual performance capabilities that have been purpose-designed for a specific application and so will offer enhanced installation and operational benefits, when compared to traditional systems.

It is important for manufacturers and suppliers of plastic products to come together and educate the building services industry on their performance capabilities and the benefits they can offer specifiers, contractors, installers and end users.

Des Dolan is Durapipe's Building Services Brand Manager