System Boiler & Unvented Cylinder Installation across London & Kent
Strong mains-pressure showers in every bathroom, even with two running at once. Our own G3-qualified Gas Safe engineers install system boilers with unvented hot-water cylinders across South East London and North West Kent, with a fixed written quote before any work starts.
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 System Boiler With an Unvented Cylinder Right for Your Home?
A combi heats water as you use it, which works well in smaller homes. In a house with two or more bathrooms, it struggles when several taps or showers run together.
A system boiler heats a cylinder of stored hot water. An unvented cylinder runs at mains pressure, so every shower gets strong flow, with no cold-water tank in the loft and no pump.
It usually suits homes with:
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two or more bathrooms or en-suites
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several people showering at the same time each morning
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an old vented cylinder and loft tanks you want removed
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weak shower pressure on a gravity-fed system
Before we recommend it, we test your mains water pressure and flow rate. An unvented cylinder needs a strong enough supply. If your home is better suited to a combi, we’ll tell you.
Combi, System or Keep Your Existing Cylinder?
Combi Boilers
System boiler + unvented cylinder
Heat-only boiler (keep your cylinder)
Hot water on demand from one unit, with no cylinder. Best for flats and homes with one bathroom. Flow drops if two outlets run at once.
Stored hot water at mains pressure. Best for larger homes with 2+ bathrooms. Needs a G3-qualified installer, a safe discharge route and an annual cylinder service.
Replaces the boiler and keeps your existing vented cylinder and loft tanks. Simplest where pressure isn’t a problem and the cylinder is in good condition.
G3 Qualified
Unvented cylinders must be fitted by a G3-qualified installer under Building Regulations. Our G3 engineer handles every unvented installation and notification.
Why Choose GX7 for System & Unvented Installations?
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 cleaned and protected before handover.
What's Included in Every Installation
Home Survey
Hot-water demand, mains pressure and flow tested before we recommend anything.
Sized to Your Home
System boiler and unvented cylinder matched to your bathrooms and household.
Safety Components
Expansion vessel, safety valves, tundish and discharge pipe fitted to regulations.
Controls & Zoning
Programmer, thermostat and zone valves set up so you control heating and hot water separately.
System Protection
Chemical flush, inhibitor and magnetic filter to protect the new boiler.
Old System Removed
Old boiler, cylinder and loft tanks taken out and disposed of.
Commissioning & Notification
Benchmark completed, and G3 and Building Regulations notified.
Guarantee Registered
We register your boiler and cylinder guarantees with the manufacturer.
System boiler and unvented cylinder installations typically cost £5,000–£7,500, depending on cylinder size, pipework and controls. Fixed written quote after a free survey. See all boiler prices →
How Your Installation Works
1
Free Survey
We check your radiators, hot-water demand, mains pressure, flow rate and where the cylinder discharge pipe can run.
2
Fixed Written Quote
A clear recommendation, cylinder size and price, with no hidden extras.
3
Installation
Usually 2–3 days. We agree any time without hot water with you in advance.
4
Commissioning & Handover
Benchmark completed, G3 notified, guarantees registered and controls explained.
5
Aftercare
Your cylinder needs an annual service to stay safe and in guarantee. We'll remind you when it's due.
Boilers, Cylinders & Guarantees
We fit system boilers from Vaillant and Worcester Bosch, as well as Ideal, Glow-worm and Baxi, paired with quality unvented cylinders sized to your home.
Worcester Bosch Installer & Vaillant Advance Installer
System Boilers
Vaillant ecoTEC plus system Worcester Bosch Greenstar system Glow-worm Energy system
Ideal Logic system boilers
Baxi system boilers
Unvented Cylinders
Megaflo, JAB, Center and others. As a guide: 150 L for one bathroom, 210–250 L for two, and 300 L or more for three or more. Sized at survey.
Guarantees
Up to 10 years on selected boilers, or up to 12 years on selected Worcester Bosch models (manufacturer terms apply). Cylinder guarantees depend on model and annual servicing.
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
System Boiler & Unvented Cylinder FAQs
Ready for Strong Showers in Every Bathroom?
Book a free survey with our G3-qualified Gas Safe engineers.
Gas Safe Registered
Clear Written Quotations
G3 Qualified
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 System Boiler Survey
Tell us how many bathrooms you have and what you have now (combi, system or tanks in the loft). Photos of your boiler and cylinder help us prepare.
Get a straightforward quotation from our Gas Safe Registered heating engineers.