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.
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.
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
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
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.
Genuine reviews from ComGas customers, submitted through Google.
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Nick
3 September 2026
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Matt from ComGas Services UK Ltd was very professional, polite, friendly and quick installing a new shower in my bath (and at a better height for me) and a much easier press-in plug for my sink! He left the place spotless. This is the kind of service and installation people dream about - a 5 star service (see photos).
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Laura Peters
17 August 2026
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I have used Comgas twice and both times have been very happy with the service. Very friendly and honest. The most recent time, the job turned out to be a lot bigger than they initially thought but it was no issue and Paul stayed the extra time to make sure the job was done properly! He was really tidy, took a lot of care with the work that was done and took the time to explain what he was doing and why. Pleased to have found a reliable heating company!
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James Ross
8 August 2026
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I had an issue with my boiler and Matt came out to have a look the same day and managed to fix it. Great, professional service. Highly recommend.
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Ian Chevalier
11 June 2026
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First time we've used this company and it won't be the last. Very professional and efficient in everything they do and Matt was excellent in his knowledge and efficiency when dealing with our gas and plumbing problems.
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Karen Flackett
20 May 2026
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Excellent service. Matt came & fitted 2 taps & waste pipes he was polite & friendly & carried out the work efficiently & in a timely manner.
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Paul Norris
30 April 2026
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Fantastic experience from the chaps at ComGas! Special thanks to Matt who removed an old boiler and replaced with a new energy efficient to satisfy the demands of a five bed house with a few bathrooms/baths and showers. The ComGas admin team and Lee were fantastic too on the booking and administration side of things!
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Julie Galvin
21 April 2026
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Here at St Joseph's we have worked with Comgas for a number of years. They have completed big projects and undertake regular maintenance for our school. They price fairly, and their work is completed to a very high standard. All the engineers carry a DBS which makes life so much easier when trying to book an engineer visit.
On the rare occasion that we have an emergency I can trust that Lee will get one of his engineers to respond quickly and efficiently.
Nothing is too much trouble and no job is too small.
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Chesca Haley
16 April 2026
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Lee and the team are amazing! So helpful, so knowledgeable and really look after their customers. Highly recommend.
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Sarah Rogers
6 April 2026
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Absolutely amazing service, always a thorough job and very knowledgable. Really nice guys too. Lee has sorted numerous issues at work and around our house. We have recommended to friends and family who are also very happy
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Alison Molan
25 March 2026
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Lovely engineers, Matt and Jack, were a pleasure to have in the house. Thorough, knowledgeable, tidy and polite. Would highly recommend.
Gas purging FAQs
Questions about commercial gas purging
Common questions about what gas purging involves and when it applies.
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.