Multiple choices in a material world


Antony Corbett, Product Manager for Supply Piping Systems at Geberit, takes a look at the challenges facing building services engineers during the material selection process

Material selection is critical when designing a building’s supply piping system.

Antony examines why multi-layered piping is proving to be a popular choice for the supply of heating and potable water.


Specification challenges

Ensuring a safe, compliant and efficient supply system starts with selecting the right products for the right project. Doing so can support the energy efficiency of a building, ensure compliance to regulations, minimise running costs and, importantly, deliver a better environment for the end-user.

Material selection is critical when looking at the impact that incorrect material choices can have upon a project. Faulty fittings, burst pipes, corrosion and a heightened chance of Legionella are all risks that need to be highlighted. This needs to be considered alongside the importance of keeping project costs down, with the ONS’s construction output price index for all work increasing by around 11% since 2015.

Material choice

Since the 1940s (and particularly since the 1969 ban on lead piping in UK properties), copper has been widely used due to its inherent stability and strength, together with its resistance to the effects of heat and pressure; and its hygiene properties

In the 1980s and 1990s plastic piping emerged as an inexpensive alternative to metal pipework systems with benefits including flexibility, ease of installation and resistance to freezing.

Both remain popular.

In 2007, some 90% of new domestic properties were built using types of plastic piping for the hot and cold plumbing system, although copper remains to be a commonly selected material for all pipework, in particular for high-rise projects.

Another option is becoming increasingly popular.

Driven by cost, reliability and ease of installation, more building services engineers are turning to multi-layer composite pipes. These can be a strong, flexible and added-value option for building services across any project.

Multi-layered piping

First introduced to the UK in the 1970s, multi-layered piping systems have often been reserved for industrial applications, such as process water. However, they are now also proving popular as a solution for potable water and heating supplies on both commercial and domestic projects.

Multi-layered piping consists of three layers

  • An outer plastic layer usually made of polyethylene (PE-RT II for Geberit Mepla) which protects against corrosion and mechanical damage. Non-reactive and flexible. Cross-linked polyethylene (PE-X) and high-density polyethylene (HDPE) can also be used.
  • An aluminum layer which makes the pipe stable but able to be bent. Typically, 0.2-0.7mm thick; depending on pipe diameter
  • An inner plastic layer, which is usually made from the same or similar material to the outside layer.

The aluminium layer offers mechanical stability to ensure that the pipe remains in its required position once bent into position. Opting for a multi-layer piping system such as Geberit Mepla will therefore offer enhanced strength and durability when compared with plastic piping and will be lighter than most metal options.  

Key benefits

In the first instance, opting for multi-layer piping can result in a more efficient installation process. These systems use press-fit technology, so they eliminate the requirement for hot works. The only tools needed to form a reliable and tight connection are a cutter, deburrer and pressing tool.

Another benefit these systems can offer professionals is they can be adjusted to the on-site conditions. Can even be manipulated to follow the line of any curved architectural features in buildings. Pipes of 16mm and 20mm can be bent effortlessly by hand and larger diameters can also be bent without risk of de-lamination or kinking with use of the appropriate tool. This can significantly reduce the number of fittings required and can, therefore, increase installation speed.  In many cases this can result in a significantly lower overall project installation cost when compared to other methods.

Finally, the construction of multi-layer piping means that professionals can have complete ease of mind that the system will not leak. A system from a reputable manufacturer will also have a leak-path method for checking of unpressed joints.

Overcoming material challenges

It’s not just the ease of installation that is seeing these systems grow in popularity. Multi-layered piping can also overcome many of the common specification challenges faced by industry professionals.

  • Corrosion resistant - Multi-layer systems are suitable for cold water systems with no need for additional measures to prevent corrosion. The polyethylene inner layer is resistant to cracking, aging and general wear and tear, and is non-reactive and corrosion resistant
  • Hygienic - The low internal surface roughness makes it more difficult for limescale and biofilm to adhere to the smooth surface, enhancing hygiene for potable water applications  
  • Minimised risk of oxygen diffusion - The thin aluminium layer prevents the diffusion of oxygen through the pipe wall. This reduces the risk of damage by oxygen corrosion elsewhere in the system  
  • Reduced thermal expansion - The aluminium layer helps to maintain thermal expansion rate to about 10% of that of a solid PE-RT pipe, with five times less expansion than PE-X and eight times less than polybutylene pipe
  • Poor heat conductor - With thermal conductivity of 0.43 W/mK, these systems lose around 800 times less heat than copper piping
  • Acoustics - A smooth bore can ensure water passing through the pipework produces less noise than in metal piping
  • Sustainable - Multi-layer piping is 100% recyclable and requires significantly less energy to fabricate, transport and install than comparative systems (according to calculations by the European Plastic Pipe and Fittings Association)
  • Low intrinsic scrap value - Reduces the risk of theft from site, which remains a key challenge throughout the supply chain

Realising the benefits

The World Health Organisation (WHO) underlines the significance of getting material selection right when it stated that:

The durability of a plumbing system is dependent on the quality of its component parts and the assembly skills of those who install it. No plumbing system, however well designed, can be expected to operate safely or hygienically if the products or materials used are unsatisfactory.”

Keeping an open mind to product development and innovations, new materials and better ways of working is crucial – and making the right material choice from the outset will help ensure industry professionals ensure a successful and safe outcome across projects.

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