Project Overview
Plumb London was instructed to carry out a full system boiler replacement at a residential property in Greenford, UB6. The client, Sandra, had been living with an ageing Glow-worm heat-only boiler, estimated to be in excess of 30 years old, which had reached the end of its serviceable life. A hot water cylinder was also present on site, forming part of the existing open-vented system.
Following an initial survey and a period of preparation while the property was readied, works were scheduled and completed over two days in June 2026. The old boiler, flue and associated components were fully decommissioned and replaced with a new Vaillant system boiler, accompanied by a complete controls upgrade, new magnetic filtration, and a full chemical flush of the central heating system.
The result is a modern, efficient and fully compliant heating system, professionally installed, Gas Safe registered, and backed by a 10-year manufacturer’s warranty.
The Client’s Brief
Sandra had a clear brief: replace her failing, outdated Glow-worm boiler with a new Vaillant appliance, a brand she had specifically requested. Her wider priorities included:
- Reliable, energy-efficient heating backed by a strong manufacturer warranty
- Retention of the existing hot water cylinder arrangement, suited to her property’s layout
- Upgraded heating controls for improved ease of use and temperature management
- A clean, tidy installation with all pipework neatly concealed
- Full certification, Gas Safe registration, and regulatory compliance on completion
Our Survey & Recommendations
We carried out an initial site visit to assess the property and existing heating system. The survey confirmed that the Glow-worm heat-only boiler was at least 30 years old, significantly beyond its expected service life and no longer suitable for repair or continued operation.
The high-level cupboard position was identified as the most appropriate location for the new boiler, making efficient use of the available space while enabling a neat, accessible installation. New flue routing was assessed, with a core hole required to accommodate the updated termination point.
The condition of the heating system indicated that a full chemical flush in accordance with BS 7593 regulations would be needed before connecting the new appliance, a standard protective measure to clear any accumulated sludge and magnetite deposits from the ageing pipework. The survey also identified the opportunity to upgrade the controls as part of the project, including a wireless room thermostat and a repositioned programmer.
Planning & Preparation
We first attended the property in August of the previous year, but the installation couldn’t proceed at that stage as the property needed clearance before works could take place. The project was paused pending confirmation that the site was ready.
Once the property was prepared, we revisited in March 2026 to reassess the scope and issue an updated quotation. Following the client’s approval of the revised proposal, works were confirmed and scheduled for June 2026. This structured approach meant that when the team arrived on site, all logistics, materials and planning were in place, allowing the project to proceed efficiently and to programme.
The Work We Carried Out
- Isolated all necessary supplies and carried out a full system drain-down
- Decommissioned the existing Glow-worm boiler, flue and associated components
- Carried out a full chemical flush of the central heating system in accordance with BS 7593 regulations
- Supplied and installed a new Vaillant system boiler in the high-level cupboard position, with new flow, return and gas pipework routed through the worktop
- Cored a new flue aperture and fitted a complete new flue system with all accessories and plume management kit, installed to manufacturer’s specifications
- Adapted the condensate drainage arrangement, including supply and installation of a condensate soakaway or condensate pump, terminating correctly to current standards
- Cut into the system return and fitted a new magnetic filtration unit to protect the heat exchanger
- Refilled the central heating system and dosed with scale inhibitor
- Supplied and fitted a new UPS4 pump with associated wiring, routed from the cylinder cupboard to the boiler location using trunking
- Wired the installation to Part P and Gas Safety (Installation and Use) Regulations requirements
- Supplied and connected a wireless DT4 room thermostat and new programmer in a relocated position
- Supplied and fitted new boxing to conceal exposed pipework to a professional finish
- Supplied and fitted a new carbon monoxide detection alarm
- Tested the existing gas supply for soundness
- Inspected all radiators for heat emission and carried out system balancing as required
- Demonstrated correct operation of the new system and controls to the client
- Commissioned the installation and completed all Benchmark documentation
- Notified Local Building Control and registered the installation with Gas Safe
- Completed a Domestic Gas Safety Certificate
- Removed all waste materials and left the site clean and tidy
A formal written testimonial was not obtained for this project. Sandra was fully satisfied with the completed installation, was present throughout the works, and confirmed she was happy with the result following the post-installation demonstration of her new system and controls.
Timeline & Completion
Works commenced on 22 June 2026 and were completed on 23 June 2026, a two-day programme, as planned. The installation team attended site from 8am on the first morning, with works carried out by a lead engineer supported by a specialist assistant. The project was delivered on programme and in full, with no reported overruns, and the client’s home was left clean and tidy at the close of each working day.
Challenges & How We Solved Them
An extended lead-in period
The project had an unusually long pre-installation period, first assessed in August before works could proceed. Rather than treating this as a straightforward delay, we maintained engagement with the client, returned to site once it was ready, and issued a fresh, accurate quotation, so Sandra received correctly priced works with no surprises on the day.
Ageing system and pipework condition
A boiler in excess of 30 years old carries a significant risk of sludge and magnetite accumulation in the associated pipework. We carried out a full BS 7593-compliant chemical flush and installed a magnetic filter on the return for ongoing system protection, safeguarding the new boiler’s heat exchanger from day one.
Boiler repositioning and new pipework routing
Installing the new boiler in a high-level cupboard position needed new pipework routed through the worktop and a new flue aperture cored. The works were planned in advance and executed neatly, with all new pipework concealed behind purpose-built boxing.
Controls upgrade and electrical compliance
Upgrading and relocating the controls, including a wireless room thermostat and repositioned programmer, needed careful electrical planning. All wiring was installed to Part P and Gas Safety Regulations requirements, with new pump wiring neatly routed from the cylinder cupboard using trunking throughout.
The Finished Result
On completion, Sandra was left with a fully modernised central heating and hot water system. A brand new Vaillant system boiler sits cleanly in its high-level cupboard position, all pipework neatly concealed, with new controls providing intuitive management of heating and hot water throughout the property.
The entire system was flushed, filtered, chemically dosed and balanced before handover. All documentation was completed, the installation registered with Gas Safe, a Domestic Gas Safety Certificate issued, and Sandra given a full demonstration of her new controls before the engineers departed. The transformation from a 30-year-old failing appliance to a modern, warranted and fully compliant heating system represents a significant, lasting improvement to the property, delivering improved efficiency, reliability and peace of mind for years ahead.
Project Investment
Pricing for a project of this scope depends on the condition of the existing system, the works required, and the final specification agreed with the client. Contact us for a tailored quotation. This kind of full system boiler replacement delivers a fully compliant, modern heating system backed by a 10-year warranty, together with the long-term efficiency gains of replacing a 30-year-old appliance. Weighed against the avoidance of escalating repair costs and the risk of an unplanned breakdown, the value is clear.
Why Choose Plumb London
- Gas Safe registered engineers, fully qualified and experienced across all major boiler brands and system types
- End-to-end project management from initial survey through to commissioning and certification
- Transparent, detailed quotations with no hidden costs
- Respectful of your home. All works carried out cleanly, with waste removed on completion
- Full regulatory compliance as standard. Gas Safe registration, Building Control notification and Benchmark documentation completed on every installation
- Aftercare support and access to manufacturer warranties for long-term peace of mind
- A trusted London family business with a commitment to quality over volume
Frequently Asked Questions
What is the difference between a system boiler and a combi boiler?
A system boiler works alongside a hot water storage cylinder, making it well suited to homes with higher hot water demands or multiple bathrooms. A combi boiler heats water on demand without a cylinder, which suits smaller properties. For Sandra’s property, retaining the existing cylinder and upgrading to a modern system boiler was the most practical and cost-effective approach.
Why is a chemical flush necessary when replacing a boiler?
In any heating system, particularly one that’s been in service for many years, sludge, scale and magnetite can accumulate in the pipework and radiators. Connecting a new boiler to an uncleaned system can damage the heat exchanger and significantly reduce efficiency. A chemical flush carried out to BS 7593 standards, combined with a magnetic filter, protects your investment from the outset.
When should a powerflush be carried out?
A powerflush is recommended whenever a new boiler is being connected to an existing system, as it was here, since old pipework almost always carries some degree of sludge or scale build-up regardless of how the system has been maintained. Beyond a new installation, it’s also worth considering if radiators are cold at the bottom but hot at the top, if the system is noisy, if circulation feels sluggish in parts of the property, or if it’s simply been several years since the system was last cleaned. Our engineers assess this at survey stage and will only recommend a powerflush where it’s genuinely needed.
How long does a system boiler replacement typically take?
A straightforward system boiler replacement is typically completed within one to two days. Sandra’s installation, which included a controls upgrade, new pump, condensate adaptation and decorative boxing, was completed comfortably within the planned two-day programme.
What certification will I receive following a boiler installation?
Every installation we carry out includes Gas Safe registration, notification to Local Building Control under Part P, a completed Benchmark commissioning document, and a Domestic Gas Safety Certificate. You’ll also receive your manufacturer’s warranty documentation, in this case, Vaillant’s 10-year warranty.
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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.
