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Technical Library: Gasfitting


Multi layer pipe systems for indoor gas installations

Energy Safety reminds gasfitters using multilayer pipe that AS/NZS 5601 has specific requirements on its use in installations. In addition, they have modified the Electricity and Gas High Risk Database so installations where multilayer pipe is used outdoors can be recorded.
Multilayer (or “PEX”) piping is becoming increasingly popular with gasfitters for installing as pipework in gas installations. Multilayer piping is a sandwich of an outer layer of cross-linked polyethylene (“PEX”), a middle layer of aluminium and then another inner layer of the cross-linked polyethylene.

It is easy to bend and joints are made by crimping the pipe end to a metal fitting using a crimping tool. It is also cheaper than the traditional copper piping once the initial outlay for the special tools has been covered.

However, the piping has limitations. The plastic used in its composition has no ultraviolet resistance and typically has a maximum temperature rating of 40–70°C. It must therefore not be used outdoors without protection and can’t be used too close to a hot gas appliance.

Each brand of piping is proprietary and has its own fitting and crimping tools - the different systems are not interchangeable.

The installation standards recognise these limitations. The installation standard 5601.1 has several specific sections that deal with proprietary multilayer piping systems.

- Section 4.5.4 requires that the system is identified with a label at the point of supply.

- Table 4.1 prohibits the use of multilayer piping as the final appliance connection and it may not be used where temperatures exceed 60°C.

- Section 5.2.13 requires that for some classes of installation, a multilayer piping carcass, must have “reversion fittings” to allow another form of piping to be joined to it.

- Section 5.3.17 requires that multilayer piping above ground must be protected from ultraviolet light and physical damage.

- Section 6.6.1 also prevents the use of multilayer piping as the final connection to an appliance.

The caravan and boat standard 5601.2 does not allow the use of multilayer piping, unless the piping system is specifically designed and has product certification that includes use in caravan or boat installations.

Energy Safety recently surveyed New Zealand importers of multilayer piping to establish each firm’s approach to these requirements in the installation standard and a report on the findings is being prepared.

In the meantime, Energy Safety reminds gasfitters they must comply with the standard and the manufacturer’s instructions.

Certifying gasfitters entering a high risk record on the Electricity and Gas High Risk Database should note that there is now a tick box entry for the exterior use of this piping in the Work Specific Details section of the form.

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