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.
Lucie Victoria
15 May 2025
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Excellent service, highly recommend
James Mowat
30 April 2025
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Incredible service — problems fixed perfectly once again.
Lee, Paul and the team at COMGAS are fantastic. They arrived on time and got straight to work, quickly identifying the root cause of the plumbing and heating issues I was experiencing.
The problems were diagnosed swiftly, I was kept fully informed throughout, and both issues were fixed with impressive speed and precision.
Having worked in the industry for nearly 20 years, I know how rare it is to find reliable, trustworthy, and genuinely skilled professionals — let alone a team this good.
I joked about it at the time, but it’s true: I had the best shower I’ve ever had in this house after they finished the job — and I’ve lived here for 10 years!
I honestly couldn’t ask for more and can’t recommend COMGAS highly enough.
Faz
31 March 2025
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ComGas replaced my boiler and water tank at short notice. So glad i used them. Thank you
Laura Andrews
26 March 2025
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Lee came out to the school I work in to look at a problem with our heating, he diagnosed the issue and was able to fix it on the spot in a neat and tidy manor. Would highly recommend
Chloe
26 March 2025
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I recently used Comgas for a gas and heating service, and I couldn't be more impressed! From start to finish, their team was professional, friendly, and highly knowledgeable. They quickly identified the issue with my heating system and explained everything in detail, offering both short- and long-term solutions.
The technician was punctual and took extra care to ensure everything was running smoothly. I really appreciated their attention to detail and how they made sure to clean up after the work was completed. My home is now warm and cozy, all thanks to their expert service. I highly recommend Comgas for anyone looking for reliable, efficient, and trustworthy gas and heating professionals!
Bec Newey
8 July 2024
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Messaged Lee on a Sunday evening with request. Instant reply that evening and engineer came next day. Polite, professional and helpful. Thorough investigation and speedy resolution to a leak with sink in wc. Happy customer.
P Duffy
2 April 2024
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Scott and the team have served me well over several years. Skilled craftsmen. Dependable careful and very cosy-effective. I highly recommend them.
Cilla Trout
22 March 2024
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Definitely recommend friendly reliable service
Scott was helpful and reassuring regarding our boiler answered our concerns and explained the problem and best course of action thank you for your advice
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.