Project Overview
A long-standing Plumb London client in Twickenham, TW1, contacted us after their combi boiler developed a leak and stopped operating reliably. The boiler, an Ideal 24 Combi originally installed by Plumb London back in 2018, had reached a point where repair was no longer the appropriate course of action.
Following an engineer visit and thorough on-site inspection, a serious safety concern was identified. The system was immediately decommissioned, and a full boiler replacement was carried out using a new Glow-worm Compact 24kW combi boiler, complete with a new flue, system protection filter, scale reducer, and carbon monoxide detector. Works were completed to Gas Safe and current building control standards, leaving the client with a safe, efficient and fully warranted heating system.
The Client’s Brief
The client’s primary concern was restoring safe, reliable heating and hot water as promptly as possible. Having previously used Plumb London for the original installation in 2018, they returned to us with confidence in our workmanship and processes. Their requirements were:
- A like-for-like replacement causing minimal disruption to the existing system
- A reputable, energy-efficient boiler backed by a strong manufacturer’s warranty
- Full compliance with current Gas Safe and building regulations
- Assurance that the wider heating system would be assessed and protected as part of the works
Our Survey & Recommendations
Our engineer attended site following the client’s report of a boiler leak. On arrival, the boiler had been switched off. It was powered back on for inspection purposes, during which significant moisture was found inside and around the gas valve, a strong indicator of internal seal failure.
A flue gas analysis was then carried out around the heat exchanger and flue adaptor. Results confirmed elevated levels of carbon monoxide present within the boiler casing, a critical safety finding. Our engineer immediately isolated the gas supply and removed the fuse from the boiler’s dedicated spur, rendering the unit safe. A formal warning notice was issued in line with Gas Safe procedures.
Given the boiler’s age at the time of inspection, seven years, and the severity of the findings, a full replacement was recommended over any attempted repair. The heat exchanger deterioration and associated carbon monoxide risk made continued operation wholly unacceptable.
Planning & Preparation
We prepared a detailed quotation following the site inspection. The full scope of works, including the chemical flush, system protection filter, scale reducer and carbon monoxide detection, was clearly outlined, so the client understood what was included and the purpose of each element. Given the safety-critical nature of the situation, works were scheduled promptly following approval. As a returning client with an established relationship with Plumb London, the process from inspection through to sign-off was straightforward and efficient.
The Work We Carried Out
- Isolated necessary supplies and drained down the central heating system
- Decommissioned the existing Ideal 24 Combi boiler, flue and associated components
- Carried out a full chemical flush in accordance with BS 7593 regulations
- Supplied and installed a new Glow-worm Compact 24kW combi boiler
- Supplied and fitted a new horizontal flue with all necessary accessories to current standards
- Altered pipework to accommodate and connect to the new boiler
- Made all appropriate plumbing and electrical connections
- Adapted the existing condensate arrangement to suit the new appliance
- Cut in and installed a new 22mm boiler protection filter on the return
- Cut in and installed a new 15mm inline scale reducer on the incoming mains
- Refilled the central heating system and dosed with scale inhibitor
- Wired the boiler to Part P and Part L requirements
- Connected onto existing controls, confirmed fit for purpose
- Supplied and fitted a new carbon monoxide detection alarm
- Tested the gas supply for tightness
- Inspected radiators for required heat emission and balanced the system as necessary
- Demonstrated correct operation of the new system and controls to the client
- Commissioned the installation and completed Benchmark documentation
- Notified Local Building Control and registered the installation with Gas Safe
- Removed all waste materials, leaving the site clean and tidy
A formal written testimonial was not obtained for this project. The client's decision to return to Plumb London for their boiler replacement, having placed their trust in us for the original installation seven years earlier, speaks for itself. The client expressed full satisfaction with the service provided and the speed with which the situation was safely resolved.
Timeline & Completion
The replacement was completed in June 2025. Given the safety-critical circumstances, with the original boiler isolated due to carbon monoxide risk, scheduling was prioritised to minimise the time the client was without heating and hot water. The full installation was carried out and completed within a single working day, on time and in line with the agreed scope.
Challenges & How We Solved Them
Carbon monoxide risk identified on site
Flue gas analysis readings taken around the heat exchanger and flue adaptor revealed elevated carbon monoxide levels, a finding requiring immediate action. Our engineer followed Gas Safe At Risk procedures without hesitation: gas was isolated, the spur fused out, and a formal warning notice issued before leaving the property. This swift, protocol-driven response ensured the client’s safety and full regulatory compliance from the outset.
System contamination and long-term protection
Installing a new boiler onto an existing system without addressing residual sludge and scale is one of the most common causes of premature appliance failure and voided warranties. A full chemical flush was carried out in accordance with BS 7593, the system was dosed with inhibitor on refill, and both a 22mm boiler protection filter and a 15mm inline scale reducer were fitted, giving ongoing, multi-layered protection for the new boiler.
Pipework adaptation
Replacing a boiler on an established installation rarely amounts to a straight swap. Pipework alterations were needed to align with the Glow-worm Compact’s connections and to accommodate the updated condensate arrangement. These adaptations were planned and executed cleanly, maintaining the integrity of the existing installation while meeting current standards throughout.
The Finished Result
The client now has a modern, high-efficiency Glow-worm Compact 24kW combi boiler, fully installed to Gas Safe and building control standards and backed by a five-year manufacturer’s warranty. The system has been chemically flushed, balanced and treated with inhibitor, protected from the inside out.
A new carbon monoxide detector has been installed in the property, giving an additional, permanent layer of safety. The client was given a full walkthrough of their new system before our engineers left site, and all documentation, Benchmark certification, Gas Safe registration and building control notification, was completed as part of the works.
This project also reflects something we’re genuinely proud of at Plumb London: a client who trusted us with their original boiler installation in 2018 chose to return to us again in 2025. That kind of loyalty isn’t taken lightly, and it reinforces our commitment to quality workmanship and honest, straightforward advice on every single job.
Project Investment
Total investment: £2,296.00 plus VAT, covering the complete supply and installation of a new Glow-worm Compact 24kW combi boiler, including a new flue, full system flush, boiler protection filter, scale reducer, carbon monoxide detection, Gas Safe registration and building control notification. A comprehensive installation with no hidden costs and no corners cut.
Why Choose Plumb London
- Gas Safe registered engineers with extensive experience across residential and commercial heating installations
- Transparent, itemised quotations. Every element of the work is explained before a single tool is picked up
- Every installation is fully compliant with Gas Safe, Part P, Part L and building control requirements
- Benchmark documentation, Gas Safe registration and building control notification included as standard on all boiler replacements
- We protect your system as well as replacing your boiler. Filtration, chemical flushing and inhibitor treatment come as part of the package
- We build long-term relationships with our clients, not just one-off transactions, as this project demonstrates
Frequently Asked Questions
How do I know if my boiler needs replacing rather than repairing?
Age, fault type and safety are the three key factors. A boiler over ten years old with a significant internal failure, particularly one involving a carbon monoxide risk, is generally more cost-effective and considerably safer to replace than repair. Our engineers will always give an honest assessment, we will never recommend a replacement if a repair is the right call.
What should I do if my boiler has been condemned or issued a warning notice?
Do not attempt to restart or tamper with the unit. A Gas Safe warning notice means the boiler has been identified as a safety risk and must not be operated until the matter has been resolved by a registered engineer. If you have any concerns about carbon monoxide in your home, open windows, leave the property, and call the Gas Emergency line on 0800 111 999.
What is a chemical flush, and why is it included?
A chemical flush removes sludge, scale and corrosion debris from your central heating system using specialist cleaning agents, carried out in accordance with BS 7593 regulations. Installing a new boiler onto a contaminated system is a leading cause of premature failure and can void the manufacturer’s warranty. We include it as standard on all boiler replacements for exactly this reason.
How long does a boiler replacement take?
The majority of residential boiler replacements are completed within a single working day. More involved installations, where significant pipework alterations, system upgrades or access challenges are present, may require two days. We always provide a clear, realistic timeframe before any works begin.
What is a flue gas analysis and why is it carried out?
A flue gas analysis measures the composition of the gases produced by a boiler during combustion, including carbon monoxide levels, to check the appliance is burning gas safely and efficiently. It’s a standard part of any thorough boiler inspection, and it’s often how a hidden safety fault, one with no obvious symptoms, gets caught before it becomes dangerous. In this case, it was the flue gas analysis that identified the elevated carbon monoxide levels behind the boiler casing.
What happens when a Gas Safe engineer issues an ‘At Risk’ warning notice?
An At Risk notice is issued when a gas appliance is found to be unsafe to continue operating, but doesn’t need to be immediately disconnected from the gas supply by law (as opposed to an Immediately Dangerous notice, which does). The engineer isolates the specific fault, in this case by removing the fuse from the boiler’s dedicated spur, and advises the homeowner not to use the appliance until it’s repaired or replaced. It’s a formal, recorded safety step, not just advice given verbally.
Is seven years old too young for a boiler to need replacing?
It’s younger than average for a full replacement, most boilers are expected to last 10 to 15 years, but age isn’t the only factor. A safety-critical fault, such as a cracked heat exchanger or carbon monoxide leak, can make replacement the right call regardless of a boiler’s age, since the cost and risk of a serious fault outweighs the appliance’s remaining expected lifespan. In this case, the finding was severe enough that repair was never a realistic option.
Can I go back to the same company that installed my original boiler for a replacement?
Yes, and it’s often the simplest option. A company that installed your original system, or has serviced it since, already has a record of your property and its history, which can make diagnosis faster and more accurate. In this case, the client’s original installation was carried out by Plumb London in 2018, and returning to us for the replacement in 2025 meant no time was lost re-explaining the property’s history.
What warranty comes with a Glow-worm Compact boiler?
The Glow-worm Compact range carries a 5-year manufacturer’s warranty when installed and registered by a Gas Safe registered engineer. Our engineers handle registration as part of every installation, so the warranty is active from day one.
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Customer Testimonials
Don’t just take our word for it, here’s a selection of the latest reviews. You can view more here.
Excellent service by Plumb London, fixed two bathroom related issues in a couple of days - clear communication and good management of expectations in terms of works and timeline, which I always apprec..Read More
Sandra Obradovic
Really happy with the service from Plumb London for my toilet repair. We're quick to attend and Charlie was very knowledgeable, getting the specific part needed and even providing advice on some other..Read More
Darren Phillips
Plumb London were brilliant from quote to completion. Firstly, they are very competitively priced and I had very little hesitation going with their quote for a new boiler. I was also really impressed ..Read More
Ashley Watkinson
Our boiler was leaking and Nicola fixed it the day it happened. Highly recommended!
Kathy Weston
Brilliant service, friendly engineer and a job completed quickly and tidily. I would use the company again if I ever need to. Swanscombe, Kent
Collin Best
Plumb London were able to come quickly and fix my problem without fuss, quoting a sensible price.
Robert Slater
My toilet seat was broken and previous plumbers I contacted told me it was a non-standard toilet and I had to get a new toilet. I invited over Plumb London and they told me that the toilet seat can be..Read More
Geoffrey Payne
Plumb London provided excellent service from start to finish! The boiler installation was quick, tidy, and professionally done. A year later, the same engineer carried out an efficient and thorough ma..Read More
George Ezeanaka
Fantastic experience all around. The customer service team at PlumbLondon is not only responsive and super-friendly, but actually take initiative - we had our job done a day early because a team membe..Read More
Eleanor Franzén
Plumb London carried out a boiler and gas safety check for me. They were quick to get booked in, the team were polite and professional, and their pricing was more competitive than others I contacted. ..Read More
Louise Kaufhold
A Five Star service. The range of skills and craftsmanship displayed by Mounir were incredible. Would recommend to anyone with dreams of creating a Dream Kitchen. With this Team, it’s not just possi..Read More
Trevor Beattie
Easy to communicate with and quick work to solve the problem we had
Josh Evans
Excellent service from start to finish, everything was handled professionally and efficiently. Communication was clear throughout, and Louise did a great job coordinating everything and keeping me in..Read More
Claire Willis
Plumb London were brilliant. Stephan turned up on time, was very personable and was very efficient. Would definitely recommend and will be using again in future.
Eleanor Rider
For the second year in a row, the lovely Mo serviced our boiler. He was on time and provided a super thorough service. I would really recommend Plumb London as your plumbing company. 5 stars all round..Read More
Dianah Jane Coleman
Very fast service. We got our boiler changed as an emergency a year ago, and got service this year. Both times Plumb London were booked within 24h of being called, with the team taking good care of en..Read More
Alexandra Fleming
Great professional service from start to finish. The team did an excellent job installing a Powertank and paid close attention to detail throughout. I’ve used them a couple of times now and have alw..Read More
Kevin Senior
Absolutely exceptional service. Cannot recommend enough. Polite, attentive and understanding of the situation. Par and Stephan who attended my property were courteous and professional, making the horr..Read More
Max Hurd
I can’t fault the service I received. Prompt, courteous and so accommodating. It’s so easy to be ripped off, PlumbLondon are overwhelmingly decent, thorough and reliable. A million percent recomme..Read More
Kate Comer
Amazing job the works is done very professionally I will not hesitate to use your company again and recommend to friends.
Renato Balane
Fantastic service, efficient and easy to organise. Reliable and fair pricing
Jane Renton-Rose
Very professional and comprehensive service.
Stuart Highley
Fast service (next day) for the initial assessment of the issue. Then, even though it was not an emergency per se (needed broken shower pump replaced and associated inter-connecting pipe work), the te..Read More
Jeff Smith
a five-star service
David Akers
I had a great experience with Plumb London. They came out quickly to inspect an issue with my water tank, identified the problem right away, and got everything sorted efficiently. The engineer was pro..Read More
Patrick Fuller
Delighted with the service from Plumb London on a number of occasions. Very reliable and professional.
Thomas Jacques
good job well done boiler replacement
Deirdre Bell
Excellent service from engineer who attended to change kitchen tap. Punctual, courteous and knowledgeable. Got the job done despite an unexpected issue with some complex piping (resolved on the spot)...Read More
Constantia Smith
Contacted Plumb London hi Charlie, come round and give me a quote within days. Carried out. I ordered all the parts and even matched The new tiles with the existing. Hardly recommend them very profess..Read More
Vimal Sharma
Very professional. The work was carried out efficiently and quickly.
matt o'neill
Amazing job the works is done very professionally I will not hesitate to use your company again and recommend to friends.
Renato Balane
Fantastic service, efficient and easy to organise. Reliable and fair pricing
Jane Renton-Rose
We recently worked with Plumb London at AKA Marylebone and were extremely impressed with their professionalism and technical expertise. The project involved complex plantroom systems and ongoing comm..Read More
shellie-ann delaney
Excellent service. I've used Plumb London multiple times and they're always professional (they pick up the phone and arrive when they say they will). For example, my boiler had been leaking but only o..Read More
Sebastian Robinson
The initial consultation from Plumb London was excellent, and then a call received quickly do explain a detailed quote. The appointment for the work was quick and the work to the bathroom carried out ..Read More
Nick M
Had a new boiler installed 4 years ago, best decision. They have looked after it well and every service is efficient, quick and easy. They are fantastic to book with, always answer the phone and any i..Read More
Milly Smith
Big thumbs up for Plumb London, in particular the engineer (Andrew) who visited the property where my elderly mother lives. A gentle manner and patient approach was exactly the level of kindness that ..Read More
Patrick Totty
Prompt and efficient service from Plumb London. A clear and comprehensive quote was provided and the job was completed well. Our ancient boiler completely stopped working and they were able to visit t..Read More
Simone Thomas
Plumb London were absolutely incredible. We were in an emergency situation, and Jack did everything he possibly could to get a new boiler out to us as quickly as possible. He also liaised directly wit..Read More
Lily Macpherson
Fabulous and prompt service. Kept up to date; great communication.
Paula Kennedy
Great job, quick efficient and fair price
Daniel Dean
Delighted with the service from Plumb London on a number of occasions. Very reliable and professional.
Thomas Jacques
The service from Plumb London was prompt and they have solved the problem as I have still not had a complaint from my tenants It was very easy to deal.with the staff at Plumb London.
Shubha Kasbekar
Excellent service from engineer who attended to change kitchen tap. Punctual, courteous and knowledgeable. Got the job done despite an unexpected issue with some complex piping (resolved on the spot)...Read More
Constantia Smith
Excellent service by Plumb London, fixed two bathroom related issues in a couple of days - clear communication and good management of expectations in terms of works and timeline, which I always apprec..Read More
Sandra Obradovic
Really happy with the service from Plumb London for my toilet repair. We're quick to attend and Charlie was very knowledgeable, getting the specific part needed and even providing advice on some other..Read More
Darren Phillips
Contact Plumb London
If you are facing a plumbing, heating, boiler or drainage issue in London, do not hesitate to get in touch with Plumb London. Our friendly and knowledgeable team is ready to assist you with all your plumbing needs. Reach out to us today to schedule a consultation and experience the difference with Plumb London.
