1.1 This Standard provides a framework and a consistent approach for the arrangement of Natural Gas distribution mains, services, primary meter installations and installation pipework.

IGEM/G/1 Edition 3 supersedes the 1^st, 2^nd, 3^rd Impressions and Edition 2 (Communication 1765), of IGEM/G/1 which are obsolete.

1.2 This Standard has been drafted by a Panel appointed by the Institution of Gas Engineers and Managers’ (IGEM’s) Technical Co-ordinating Committee, subsequently approved by that Committee, the Gas Utilisation Committee, the Gas Measurement Committee and the Gas Transmission and Distribution Committee, and published by the authority of the Council of IGEM.

1.3 For the purposes of this Standard, definitions have been agreed between parties involved in the introduction of competition into metering activities in Great Britain. The Institution of Gas Engineers and Managers (IGEM) consulted appropriate regulatory bodies (HSE, Ofgem and Gas Safe Register), associations of gas transporters (GTs), suppliers and shippers, meter asset managers (MAMs), meter equipment managers (MEMs), installation pipework owners and installers and manufacturers of pipe, meters, regulators and other equipment associated with gas systems at the end of networks.

1.4 Arising from the provision in the Gas Act 1986 (as amended), metering services and, in particular, the provision of gas supply meters at gas consumers’ premises are provided by competitive service providers under the Review of Gas Metering Arrangements (RGMA).

In order to facilitate the operation of the market and to provide necessary controls, a number of industry documents were published which included:

• OFGAS Gas Metering Definitions

• OFGAS Codes of Practice, CoP1/a, 1/b and 1/c, which specify standards and processes applicable to meter installations
• MAM Code of Practice (MAMCoP/MCoP)

IGEM/G/1 Edition 3 builds on the above documents to provide additional and supplementary detail to assist parties who have statutory duties under legislation in the development of arrangements and to assist in the provision of a safe and secure supply of gas to consumers.

Note:       AMICOP replaced CoP 1/a,1/b and 1/c. AMICOP and MAMCOP were then replaced by MCoP as at 1st January 2021

• 5. In defining the boundaries between the Network, the primary meter installation and installation pipework, there are repercussions with respect to the boundaries of responsibility between a GT/gas conveyor with network management responsibilities, the primary meter installation owner/MAM/MEM and the installation pipework owner/operator. Notwithstanding the Notes (below), the document is consistent with the intent of current editions of:
• Gas Safety (Management) Regulations (GS(M)R)
• Gas Safety (Installation and Use) Regulations (GS(I&U)R)

• Pipelines Safety Regulations (PSR)
• Pressure Systems Safety Regulations (PSSR).

Note 1:    This Standard contains specific terminology, some of which has been altered for the purpose of clarity.

Note 2: This Standard does not include all possible configurations, and the law may allow deviation from the common practices shown. For example, the designation of an “emergency control” in a particular situation will, ultimately, rest on the facts of the case, that is primarily on intended use by a consumer of gas.

1.6 This Standard recognises inconsistency between relevant official CoPs, guidance to legislation, and national and industry standards, including those listed in Appendix 2.

This Standard consolidates the varied use of different terms across such publications, to provide a base for their future amendment and to represent current best practice.

Any definitions relating to this Standard but not contained within it are given in IGEM/G/4, which is free to access and download from www.igem.org.uk.

1.7 This Standard makes use of the terms “must”, “shall” and “should” when prescribing particular requirements.  Notwithstanding Sub-Section 1.10:

• the term “must” identifies a requirement by law in Great Britain (GB) at the time of publication

• the term “shall” prescribes a requirement which, it is intended, will be complied with in full and without deviation
• the term “should” prescribes a requirement which, it is intended, will be complied with unless, after prior consideration, deviation is considered to be acceptable.

Such terms may have different meanings when used in legislation, or Health and Safety Executive (HSE) Approved Codes of Practice (ACOPs) or guidance, and reference needs to be made to such statutory legislation or official guidance for information on legal obligations.

1.8 It is now widely accepted that the majority of accidents in industry generally are in some measure attributable to human as well as technical factors. People who initiated actions that caused or contributed to accidents might have acted in a more appropriate manner to prevent them.

To assist in the control of risk and proper management of these human factors, due regard should be taken of HSG48 and HSG65.

1.9 The primary responsibility for compliance with legal duties relating to health and safety at work rests with the employer. The fact that certain employees, for example “responsible engineers”, are allowed to exercise their professional judgement does not allow employers to abrogate their primary responsibilities. Employers must:

• have done everything to ensure, so far as is reasonably practicable, that there are no better protective measures that can be taken other than relying on the exercise of professional judgement by "responsible engineers”
• have done everything to ensure, so far as it is reasonably practicable, that “responsible engineers” have the skills, training, experience and personal qualities necessary for the proper exercise of professional judgement
• have systems and procedures in place to ensure that the exercise of professional judgement by “responsible engineers” is subject to appropriate monitoring and review
• not require “responsible engineers” to undertake tasks which would necessitate the exercise of professional judgement that is not within their competence. There should be written procedures defining the extent to which “responsible engineers” can exercise their professional judgement. When “responsible engineers” are asked to undertake tasks which deviate from this, they should refer the matter for higher review.

1.10 Notwithstanding Sub-Section 1.7, this Standard does not attempt to make the use of any method or specification obligatory against the judgement of the responsible engineer. Where new and better techniques are developed and proved, they should be adopted without waiting for the modification of this Standard. Amendments to this Standard will be issued when necessary and their publication will be announced in the Journal of IGEM and other publications as appropriate.

1.11 Requests for interpretation of this Standard in relation to matters within their scope, but not precisely covered by the current text, should be either:

• addressed to Technical Services, IGEM, IGEM House, 26 & 28 High Street, Kegworth, Derbyshire, DE74 2DA; or
• emailed to technical@igem.org.uk

These will be submitted to the relevant Committee for consideration and advice, but in the context that the final responsibility is that of the engineer concerned. If any advice is given by or on behalf of IGEM, this does not imply acceptance of liability for the consequences and does not relieve the responsible engineer of any of his or her obligations.

1.12 This Standard was published in November 2025.

2.1 This Standard is applicable to all Natural Gas systems and provides a framework for the arrangement of gas distribution mains, services, primary meter installations, installation pipework and includes: 

• definitions for the end of the gas network, the primary meter installation (including any associated regulator) and installation pipework 
• illustrations of a range of standard arrangements which are deemed appropriate for the gas industry as it currently operates and which will simplify any new arrangements that are required, to ensure a safe and secure supply of gas to a consumer 
• illustrations of a range of legacy arrangements, which are not recommended with respect to their design or layout
• identification of boundaries and interfaces. 

 
Note: The definition of these boundaries and interfaces is essential so that relevant information can be exchanged between organisations and persons who have a duty to ensure a safe and secure supply of gas to premises.  
 
2.2    The term “regulator” is intended to mean “meter regulator” unless otherwise stated. 
 
2.3    All pressures are gauge pressures unless otherwise stated. 
 
2.4    Italicised text is informative and does not represent formal requirements. 
 
2.5    Appendices are informative and do not represent formal requirements unless specifically referenced in the main sections by the terms “must”, “shall” or “should”.