Conventional, System & Back Boiler to Combi Conversion
A conventional boiler to combi conversion removes the water tanks in your loft and the hot water cylinder, freeing up space and giving you hot water on demand from the mains. Our own Gas Safe engineers convert conventional (tank-fed or gravity-fed), system and back boilers to combis across South East London and North West Kent, with your mains pressure and flow tested first and a fixed written quote before any work starts.
From £2,500 with a 5-year guarantee boiler, or from £2,900 with a 10-year guarantee boiler, power flush included. Every conversion is priced after a free survey, as gas run, pipework and location vary.
Gas Safe Registered
• Google - 4.7★
• Trustpilot - Excellent
• Worcester Bosch Installer
• Vaillant Advance Installer
• Free First annual Service & wireless thermostat free where stated on your written quote
Is a Combi Right for Your Home?
A combi heats water straight from the mains as you use it, so there's no hot water cylinder and no cold water tanks in the loft. Converting from a tank-fed or system boiler frees up the airing cupboard and loft, and you never wait for a cylinder to reheat.
The trade-off: a combi supplies one main outlet well at a time. Hot water flow depends on your mains supply, so two showers running together usually won't work well.
A combi usually suits homes with:
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one bathroom, or one bathroom plus a cloakroom
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a flat or smaller house
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good mains water pressure and flow
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old water tanks and a cylinder you want removed to free up space
We test your mains pressure and flow rate during the survey. If your home has two or more bathrooms, or the supply is too weak for a combi, we'll tell you and recommend a system boiler with an unvented cylinder instead.
Which Boilers Can Be Converted to a Combi?
Conventional (Tank-Fed) Boiler to Combi
System Boiler to Combi
Back Boiler to Combi
Also called a regular or gravity-fed system. We remove the cold water tanks in the loft, the hot water cylinder and redundant pipework, then fit a combi running from the mains. Usually the biggest space gain.
Your boiler already runs sealed, but the hot water cylinder, its controls and any cold water tank feeding it are removed. The airing cupboard is freed up for storage.
Older back boilers sit behind a gas fire. We remove the back boiler and fire, cap the gas safely and fit a new combi in a suitable position. The gas run and making good the fireplace are agreed on your quote.
Why Choose GX7 for Your Combi Conversion?
Mains Pressure Tested First
We test your mains water pressure and flow before quoting. If your supply can't run a combi well, we'll tell you and recommend the right system instead.
Own Team, No Subcontractors
The engineers who survey your home are the team who install it. We are Gas Safe registered (935610).
Worcester Bosch & Vaillant
Worcester Bosch Installer and Vaillant Advance Installer. Guarantees of up to 10 years or 12 years on selected models (manufacturer terms apply).
Tidy, Planned Work
Dust sheets down, neat copper pipework, old tanks and cylinder removed, and the system power flushed and protected before handover.
What's Included in Every Combi Conversion
Home Survey
Mains pressure and flow tested, gas supply and flue route checked, and your hot water needs discussed before we recommend anything.
Combi Sized to Your Home
Combi output matched to your bathrooms, mains supply and heating needs.
Power Flush Included
Existing radiators and pipework power flushed before the new combi is connected, inhibitor added and radiators balanced.
Heating Controls & TRVs
Controls to current Building Regulations, with TRVs added where needed — shown on your written quote.
System Protection
Magnetic system filter and scale reducer fitted to protect the new boiler.
Old System Removed
Old boiler, cylinder, loft tanks and redundant pipework taken out and disposed of, with unused pipes capped off safely.
Commissioning & Notification
Benchmark completed and the installation notified under Building Regulations through Gas Safe.
Guarantee Registered
We register your new boiler's guarantee with the manufacturer.
Combi conversions start from £2,500 with a 5-year guarantee boiler, or from £2,900 with a 10-year guarantee boiler, power flush included. Every conversion is priced after a free survey, as gas run, pipework and location vary. See all boiler prices →
How Your Combi Conversion Works
1
Free Survey
We visit to test your mains pressure and flow, check the gas supply, flue and condensate route, and agree where the new combi will go.
2
Fixed Written Quote
A clear recommendation, combi size and fixed price in writing, with TRVs or any extra work listed. No hidden extras.
3
Installation
Old boiler, tanks and cylinder removed, the system power flushed and the new combi fitted. We agree the dates and any time without hot water with you in advance.
4
Commissioning & Handover
Benchmark completed, Building Regulations notified through Gas Safe, guarantee registered and your new controls explained.
5
Aftercare
An annual service keeps your combi safe and is required by most manufacturer guarantees. We'll remind you when it's due.
Combi Boilers & Guarantees
We fit combi boilers from Worcester Bosch, Vaillant, Ideal, Baxi, Glow-worm and Main, chosen to suit your home and mains supply.
Worcester Bosch Installer · Vaillant Advance Installer
Combi Boilers We Fit
Worcester Bosch Greenstar combis
Vaillant ecoTEC and ecoFIT pure
Ideal Atlantic, Logic and Vogue Max
Baxi 400, 600 and 800 combis
Glow-worm and Main combis
Sized to Your Mains
A combi can only deliver as much hot water as your mains supply allows, so a bigger boiler isn't always better. We match the output to your flow rate and bathrooms at the survey.
Guarantees
Up to 10 years on selected boilers, or up to 12 years on selected Worcester Bosch models (manufacturer terms apply). Conversions start from £2,500 with a 5-year or from £2,900 with a 10-year guarantee boiler.
Guarantee length depends on the manufacturer, model, installation and annual servicing.
★★★★★
I'm writing to express my sincere appreciation for Mr. Singh's exceptional work on my new boiler installation. He was incredibly helpful, offering various options and clearly explaining the associated costs.
His work was not only fast but also remarkably clean and tidy, with everything completed to a high standard. I am thoroughly impressed with the amazing job he did.
I would highly recommend him without hesitation for any gas related works.
A Makarov - Google review
What Our Customers Say
★★★★★
Had my boiler replaced and the whole process was effortless. Professional, efficient, and easy to work with. I will definitely recommend them 👌.
Jakin Mally - Trustpilot review
★★★★★
Harmeen and his team have done an outstanding job relocating my boiler. They were honest, reliable, and demonstrated exceptional professionalism throughout. Their thoroughness, attention to detail, and friendliness made the entire process seamless. I cannot recommend them highly enough and will certainly be using their services again. Thank you, team, for a job well done!
M. F. - Google review
Combi Conversion FAQs
Ready to Convert to a Combi?
Book a free survey with our own Gas Safe engineers. We'll test your water supply and give you a fixed written quote.
Gas Safe Registered
Clear Written Quotations
Worcester & Vaillant installers
We carry out combi conversions across South East London and North West Kent, including Grove Park, Lee, Eltham, Blackheath, Bromley, Chislehurst, Elmstead, Bickley, Petts Wood, Orpington, Chelsfield, Keston, Hayes, Beckenham, Sidcup, Sevenoaks, Otford and Westerham.
Book Your Free Combi Conversion Survey
Tell us how many bathrooms you have and what you have now (tanks in the loft, a cylinder or a back boiler). Photos of your boiler, cylinder and loft tanks help us prepare. Every conversion gets a free site survey.
Get a straightforward quotation from our Gas Safe Registered heating engineers.