Europe approved the Regulations for Construction Products in order to guarantee the performance of construction products and to ensure the fulfilment of the basic requirements for building sites. In order to do so, instructions were provided to all the CEN standardisation committees (European Committee for Standardisation) so that they could issue standardised rules, or failing that, issue European technical assessments, on the basis of which manufacturers could draw up the declarations of performance for each product, and these could be identified with the CE marking.
Since 1999, the plastic piping industry has been unable to issue a standardised rule or opt for the European method of technical assessment that would allow it to bestow the CE marking on its products or to issue the corresponding declarations of performance by means of which the manufacturers accept the responsibility for the conformity of the products with regard to their essential characteristics.
Installers and consumers need to be aware that these products do not offer the same degree of safety that they have with copper piping. The UNE standards that endorse the multi-layer system for gas installations, some of which are still being drafted, do not include tests of their behaviour in the event of fire.
According to the Gas Regulation (RD 919/2006), the authorised installer is responsible for the safety of the installation. Copper piping and its accessories has its declaration of performance, by means of which manufacturers accept the responsibility associated with their products. Nevertheless, in the event of an accident in an installation with multi-layer piping, the installer will be the only responsible party.
The multilayer systems to be introduced into the Spanish market are, in theory, endorsed by their compliance with foreign standards that are not recognised by the gas regulations and therefore do not have any regulations in Spain covering them. Project designers/installers thus assume a great responsibility if they incorporate them.
One of the arguments for the introduction of multi-layer piping is the lower cost compared to that of the equivalent copper. However, an installation consists of accessories and, in the case of multi-layer piping, the obligation to include additional safety devices. The scenario may be very different when all the elements: accessories, regulators or flow limiters, thermal cut-off devices, etc. are included. Unlike copper, multi-layer piping from different manufacturers are incompatible, and even within the same manufacturer this compatibility is not maintained over time. What will happen if the installation needs to be repaired or expanded in a few years? The manufacturers only respond when their "full system" is used. In the case of multi-layer piping, at a given moment, neither will the one intended to be used for gas be compatible with the one intended for drinking water, since the elastomers of the seals are different. Using copper will mean there will be no need to have two sets of inventories, with the consequent saving, and without the risk of using a water element for gas. The legislation currently in force does not allow the installation of gas receivers at less than 5 bar with multi-layer piping. RD 919-2006 does not yet incorporate into its list of reference standards the revision of 2014 regarding Standard UNE 60670 for domestic receiver installations that allows for the use of multi-layer piping. In addition, this Standard UNE 60670, on referring to multi-layer piping, refers in turn to UNE 53008-1 where the requirements that piping, accessories and system must fulfil are listed. However, the corresponding Standard UNE 53008-2, which establishes the requirements for the design, installation, and maintenance of these Systems, has still not been developed. Another of the messages of those promoting multi-layer piping for gas is that it is already being used in Latin America and in Germany. Although it is true that, albeit with little acceptance, it has been available in Germany since 2008, there are currently a great many technical doubts that have arisen regarding the safety of these installations for a variety of reasons such as:
- Multi-layer piping does not have a high heat resistance.
- The obligatory nature of additional thermal cut-off, regulating or flow limiting safety devices.
- In the case of these latter elements, important technical doubts arise since their original conception was not to be used as safety devices but rather as mere flow limiters, and therefore no manufacturer has been able to ensure that they would work correctly (shutting off the flow of the gas) in case of fire or partial breakage of the piping.
- The operational performance of the additional safety devices with the passage of time.
- “The real” response of these safety devices in case of fire. Their design is based on theoretical concepts that are difficult to validate. The calculation of the size of the flow limiter(s) is highly complex and inexact due to the different layouts that there can be between them and to the simultaneity with which they need to work at particular times (e.g. on starting up a boiler).
- To date, there is no additional safety device that is certified by AENOR. Moreover, there is no UNE standard nor, evidently, certification regulations either. Only Standard 60719 deals with a flow limiter designed to be installed at the input to a worktop or cooker.