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This Standard specifies the minimum requirements for the design, construction, commissioning, operation, maintenance and alteration of polyethylene (PE) or metallic mains, for the distribution of gas at pressures up to and including 16 bar.

The distribution mains system is the network of pipes which transports gas from the natural gas transmission system (see I.S. 328), LPG storage system or a gas manufacturing plant to the gas service pipes.  The installation of gas service pipes is addressed in I.S. 265.

Clause 17 deals specifically with the particular requirements for LPG systems.


This Standard has been prepared by the Distribution Technical Committee (TC 1) of the Gas Technical Standards Committee. Acknowledgement is given to the Institution of Gas Engineers and Managers Recommendations (IGE/TD/3 – Distribution Mains) which was consulted when preparing this Standard and some of its recommendations followed.

This Standard specifies the minimum requirements in respect of all aspects of the gas distribution mains system with particular emphasis on the safety requirements.  It is not a design handbook and the need for exercising competent engineering judgement is essential.

Future experience acquired in the design and construction of distribution mains and the advent of new technology and materials may lead to revisions of this Standard being issued at appropriate intervals.

Attention is drawn to the fact that legal requirements exist when laying gas mains.  In particular, all works and procedures associated with the laying of gas mains shall be in conformity with the requirements of the Safety, Health and Welfare at Work Act 2005 (and Regulations there under), and the Building Control Act 1990.

The Standard does not supersede, or take precedence over, the requirements of legislation and it is imperative that due regard be taken of such requirements.  The Standard should be applied in consultation with all relevant authorities.


For further queries please contact NSAI Standards Development