Boiler Installation
Across London —
Fitted Properly, Guaranteed.
A new boiler is a ten-year decision. We size, fit and commission combi, system and regular boilers to Gas Safe standard — with a fixed price agreed before we lift a tool, a 7–10 year manufacturer warranty on the appliance, and a written 12-month guarantee on our workmanship. Owner-led by Ian Fisher, years on the tools.
What a proper boiler installation actually involves.
A boiler installation is not a swap-and-go job. It's a full appliance replacement that has to be sized to your property's heat loss, matched to your hot-water demand, connected to compliant gas and flue runs, and commissioned to the manufacturer's Benchmark standard before it is signed off on the Gas Safe Register. Skip any of those steps and the appliance either underperforms, voids its warranty, or fails Building Regulations.
Chelsea Plumbing & Heating Co. installs combi, system and regular (heat-only) boilers across London and the Home Counties. Combi boilers suit flats and smaller homes with one bathroom. System boilers keep an unvented cylinder for households with two or more bathrooms and simultaneous hot-water demand. Regular boilers replace like-for-like where a vented cylinder and header tanks are staying in place, or where a full system redesign is not wanted.
This service is for homeowners whose existing boiler is nearing the end of its service life (typically 10–15 years), landlords who need a compliant, warrantied appliance in a let property, and buyers/sellers who need a heating system upgraded before completion. If you're getting cold radiators upstairs, rising energy bills, repeat lockouts, or a boiler that's been condemned at its last service, a replacement is on the horizon.
Why call in a specialist rather than the cheapest quote you can find on a comparison site: sizing errors, poor flue positioning, missing filters, uncommissioned controls, and unregistered installs are the four fastest ways to void a manufacturer warranty and lose thousands. Every install we hand over is Benchmark-completed, notified to your local authority via the Gas Safe Register, and paperworked for your insurer.
The cost of getting a boiler installation wrong.
An undersized boiler cycles constantly and never gets your home to temperature on the coldest days. An oversized boiler short-cycles, wastes gas, and wears out its heat exchanger years early. Both scenarios show up as higher bills and colder rooms — but the real damage is that the manufacturer will refuse warranty claims once they inspect the install paperwork.
The most expensive mistake we see is choosing a fitter on price alone. A cash-in-hand install without Gas Safe registration, Benchmark commissioning, or Building Control notification isn't legally an installation — it's a liability. If your buyer's surveyor spots it, or your insurer investigates a claim, the appliance has to come out and be re-fitted from scratch.
- ×Fitting the same size boiler as the old one instead of running a proper heat-loss calculation for the current property.
- ×Skipping a system flush or magnetic filter on a new install — voids most manufacturer warranties from day one.
- ×Positioning the flue too close to an opening window, boundary, or eaves — a fail on Gas Safe inspection.
- ×No Benchmark logbook, no Building Control notification, no Gas Safe Register entry — legally not installed.
- ×Reusing tired system components (pump, motorised valve, expansion vessel) instead of replacing on the same visit.
- ×Choosing an installer who isn't Gas Safe registered — the certificate you need at resale doesn't exist.
A methodical system,
not a rushed callout.
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01SurveyOn-site or remote survey — property size, hot-water demand, gas supply, flue route, controls.
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02Fixed quoteWritten quote with make, model, warranty length, filters, controls and labour — no surprise extras.
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03InstallRemoval of old appliance, pipework upgrades where needed, new boiler and filter fitted.
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04CommissionSystem flush, gas rate check, flue analyser test, controls set up, Benchmark logbook completed.
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05HandoverBuilding Control notified via Gas Safe, warranty registered, 12-month workmanship guarantee issued.
Concrete outcomes,
not vague promises.
Warranty that actually stands
Registered install, Benchmark logbook and magnetic filter fitted — the three things manufacturers demand before honouring 7–10 year warranties.
Right-sized for your home
Heat-loss calculation and hot-water demand assessed before we quote. No undersized combi struggling with two showers running.
Lower running costs
Modern A-rated condensing boilers with weather compensation and smart controls run 25–35% more efficiently than a 10-year-old appliance.
Legal at resale
Building Control notification lodged automatically via Gas Safe. Certificate ready for your conveyancing solicitor.
One engineer, start to finish
Ian scopes the job, fits the job, commissions the job. No sales rep, no rotating subcontractors, no lost-in-translation.
Fixed price, no VAT
Written price agreed before we start. Card or bank transfer accepted. Not currently VAT registered.
Photographs from
actual jobs.
Real installations, repairs and diagnostics carried out by Ian across London and the Home Counties. No stock photography.
Boiler types, brands and situations we install for.
Every property is different — flue routes, gas supply capacity, water pressure, radiator loading and hot-water demand all change what a good install looks like. Here's how we approach the main variations.
Combi boilers
One appliance for heating and hot water, no cylinder, no header tanks. Ideal for flats and 1–2 bathroom homes on a mains supply of at least 1 bar dynamic pressure. We commonly install 24kW–35kW combis depending on radiator count and hot-water flow-rate demand.
System boilers
Heats an unvented (pressurised) hot-water cylinder — the right answer for homes with two or more bathrooms, or where multiple outlets need mains-pressure hot water simultaneously. We're G3 Unvented qualified, which is legally required to install and commission unvented cylinders.
Regular / heat-only boilers
Retains the traditional vented cylinder and cold-water/feed-and-expansion tanks in the loft. Sensible where a full system conversion isn't wanted, where loft tanks are already in good order, or where mains pressure is too low for an unvented system.
Back-boiler removals & full conversions
Older properties often still run a back-boiler behind a gas fire. We remove, cap and re-route to a modern wall-hung condensing boiler in a kitchen, utility or airing cupboard — with pipework re-sized to suit.
System upgrades on the same visit
New magnetic filter, new mains inhibitor dose, controls upgrade (smart thermostat, weather compensation, TRVs), scale reducer where hard water demands it, and full system flush before commissioning.
Landlord installations
For let properties we coordinate with your letting agent for access, provide the tenant-facing handover, and issue a fresh CP12 alongside the install so the property is fully compliant on the day.
Manufacturer warranties
Standard install carries the manufacturer's warranty (typically 7 years, up to 10 on certain models when installed with a magnetic filter and annual servicing). We register the warranty on your behalf as part of handover — you don't chase paperwork.
How much does a boiler installation cost in London?
Straight combi swaps typically start around £2,200–£2,800 fitted, mid-range brands. Full system conversions (regular to combi, or back-boiler removal to wall-hung) run higher because of pipework re-routing and system flushing. Every job is priced in writing after a survey — no surprise extras.
How long does a boiler install take?
A straight like-for-like combi swap is typically one working day. A system conversion, back-boiler removal or full pipework upgrade is usually two to three days. We give you the exact figure at quote stage.
What warranty do I get?
You get the manufacturer's warranty on the boiler itself — typically 7 years, with 10 years available on certain models when installed with a magnetic filter and serviced annually. On top of that, Chelsea Plumbing & Heating Co. issues a written 12-month workmanship guarantee covering our installation labour.
Do you notify Building Control?
Yes. Every gas boiler install is a notifiable job under Building Regulations. As a Gas Safe registered engineer we notify your local authority through the Gas Safe Register automatically — the certificate is posted to you within 4–6 weeks.
Do you offer emergency or same-week installs?
Same-week installs are usually possible for standard combi swaps when we have the appliance in stock at merchant. Genuine no-heat emergencies are covered under our out-of-hours rate at £150/hr.
Can you install a smart thermostat at the same time?
Yes — Google Nest, Hive, Tado and Honeywell Evohome are all fitted and paired to the new boiler on install day. We include the controls in the fixed price so you know the number before we start.
Do you remove and dispose of my old boiler?
Yes. Removal, disposal, and any redundant flue/pipework capping is included in the fixed price. Site is left clean.
How long will a new boiler last?
A properly installed and annually serviced modern condensing boiler typically lasts 12–15 years. Skip the annual service and the manufacturer voids the warranty — and the appliance rarely makes it past year 8.
What areas do you install boilers in?
Greater London and the surrounding Home Counties — Kent, Surrey, Essex, Hertfordshire, Buckinghamshire, Berkshire, Bedfordshire, Middlesex and West Sussex.
Fixed price. Gas Safe.
12-month guarantee.
Free estimates from Ian directly — no call centre, no subcontractors, no surprise bills. One point of contact from first call to twelve-month follow-up.