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ComGas Services UK Ltd
Gas Safe registered engineer working on a commercial gas installation
Gas Purging

Gas Purging

Gas purging removes air from a new installation before commissioning, or removes gas from pipework being taken out of service — carried out to the appropriate procedure by Gas Safe registered engineers. ComGas provides gas purging for commercial installations across Surrey and surrounding counties.

  • Gas Safe registered engineers
  • Commissioning & decommissioning purging
  • Carried out to the appropriate procedure
  • Sequenced with testing and pipework work
A specific procedure, correctly sequenced

Purging sits between pipework work and putting an installation into service.

Gas purging is the process of safely introducing gas into new pipework to remove air before an appliance is commissioned, or safely removing gas from pipework that is being taken out of service. It is a distinct procedure from a tightness test, which checks the pipework holds pressure, and from the physical installation of pipework itself — though the three are commonly carried out in sequence on the same project.

ComGas carries out gas purging as part of new installation commissioning, following pipework alterations, and as part of decommissioning works where redundant pipework is being safely removed from service. Purging is carried out to the appropriate industry procedure by Gas Safe registered engineers, sequenced correctly with any related testing, pipework or decommissioning work.

ComGas Services UK Ltd
Commercial gas purging from Farnham, Surrey.

Gas purging services

Purging for new commissioning, alterations and decommissioning works.

We can carry out purging as its own visit, or sequenced with related pipework, testing or decommissioning work.

Commissioning Purge

Removing air from new pipework so appliances can be safely commissioned once tightness testing has confirmed the installation is sound.

  • Purging following new pipework installation
  • Carried out after a successful tightness test
  • Supports safe appliance commissioning
  • Sequenced as part of a wider installation project
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Post-Alteration Purge

Purging pipework that has been extended or altered, before the affected section is returned to service.

  • Purging following pipework alterations
  • Applied to the affected section of the installation
  • Co-ordinated with retesting where required
  • Confirmed before appliances are reconnected
Find out more

Decommissioning Purge

Safely removing gas from pipework that is being taken permanently out of service, ahead of disconnection and capping.

  • Purging as part of decommissioning works
  • Sequenced ahead of disconnection and capping
  • Carried out to the appropriate procedure
  • Co-ordinated with our Gas Decommissioning service
Find out more

Purging Following a Tightness Test

Purging carried out once a tightness test has confirmed the installation is sound, as one co-ordinated sequence of works.

  • Purging follows a passed tightness test
  • Two stages arranged as one combined visit where practical
  • Findings from both stages confirmed together
  • See our Commercial Gas Tightness Testing page for detail
Find out more
Commercial gas pipework connection point prepared for purging

Planned. Professional. Practical.

How gas purging is carried out

A controlled procedure, not simply opening a valve.

Purging is carried out to the appropriate industry procedure, using the correct rate of purge, appropriate venting arrangements and gas detection to confirm when the process is complete. For a new installation, this follows a successful tightness test and precedes appliance commissioning. For decommissioning, purging removes gas from the pipework before it is physically disconnected and capped.

Because purging involves the deliberate release or introduction of gas into a system, it is carried out only by Gas Safe registered engineers, with the area managed appropriately throughout and the completion of the process confirmed before any further step — commissioning, or physical disconnection — proceeds.

  • Carried out to the appropriate industry procedure
  • Gas detection used to confirm completion
  • Correct venting and safety arrangements observed throughout
  • Follows tightness testing on new installations
  • Precedes disconnection and capping on decommissioning works
  • Carried out only by Gas Safe registered engineers
Discuss Gas Purging
When purging is typically required

Purging sits at a specific point in most gas projects.

Purging is most commonly needed when new pipework is being commissioned for the first time, when altered pipework is being returned to service, or when redundant pipework is being decommissioned and taken permanently out of use. We can confirm whether purging applies to your specific project when we scope the work.

  • New pipework commissioning
  • Pipework alterations being returned to service
  • Decommissioning of redundant pipework
  • Following a passed tightness test
  • As part of a wider plant room or refurbishment project
  • Where an installation has been isolated for an extended period
Ask About Gas Purging

Whether purging is required, and how it should be sequenced, depends on the specific installation and works involved. We confirm this as part of scoping the project rather than assuming it applies by default.

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Gas purging FAQs

Questions about commercial gas purging

Common questions about what gas purging involves and when it applies.

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What is the difference between purging and a tightness test?

A tightness test confirms that pipework holds pressure correctly, with no leaks. Purging is the separate process of introducing gas into new pipework to remove air, or removing gas from pipework being decommissioned. On a new installation, purging normally follows a successful tightness test.

Is purging only needed for new installations?

No. Purging is also carried out when redundant pipework is being safely decommissioned and taken out of service, and following alterations to existing pipework before it is returned to use.

Can purging be combined with a tightness test in one visit?

Where the sequence allows, testing and purging can often be arranged as one combined visit, with purging following a passed tightness test. We confirm the appropriate sequence when scoping the work.

Why does purging need to be carried out by a Gas Safe registered engineer?

Purging involves the deliberate introduction or release of gas within a controlled procedure, including correct venting and gas detection to confirm completion. This requires the competence and registration of a Gas Safe registered engineer to be carried out safely.

How does purging fit into a decommissioning project?

Where pipework is being taken permanently out of service, it is normally purged of gas before it is physically disconnected and capped. See our Gas Decommissioning page for how the full process fits together.

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Need gas purging as part of a new installation or decommissioning project?

Tell us about the installation, whether it follows pipework work or forms part of a decommissioning project, and any timescale considerations.

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