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Replacing a boiler in your Earlsfield home, or fitting one for the first time in a conversion or new flat? Find a verified Gas Safe engineer covering SW18 — every listing on this page is checked as Gas Safe registered.
✅ Checked before listing — identity, insurance, trading presence, and Gas Safe registration confirmed with the Register.
✅ Workmanship guarantee badges on listings — 1, 3, 6 or 12 months
⚠️ Smell gas or suspect a leak? Call the National Gas Emergency Service on 0800 111 999 from outside — see Safety first before you book. A poorly-running gas appliance can also produce carbon monoxide.
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Coverage: Earlsfield SW18, with SW17, SW12, SW19 and SW11 edges where a listed engineer’s patch crosses the boundary. Confirm your postcode when you call.
What this covers: New and replacement gas boiler installations — combi swaps, system boilers with cylinders, boiler-type conversions, flue and condensate routing, system filtration where specified, commissioning and Building Regulations notification.
Routing steer: Repairing an existing boiler is Boiler Repair in Earlsfield; an annual service or landlord check is Boiler Servicing in Earlsfield; heating faults after the boiler are Central Heating Repair in Earlsfield.
Costs note: See What it costs for editorial estimate ranges — always get a written quote from the engineer attending.
Availability note: Installations are planned work; survey-first is normal. Confirm who handles Building Regulations notification and which water-treatment or protection measures are included in the quoted specification.
What a compliant boiler installation actually involves
A boiler install is gas work, notifiable building work and an efficiency-standards job all at once — which is why the engineer’s competence and paperwork matter as much as the boiler you choose.
Who may install it. Fitting a gas boiler must be done by a Gas Safe registered engineer. The HSE draws the boundary precisely: a non-registered person may do “wet work” — the water pipes and radiators — but work on the gas boiler itself and the final connection of the pipework to it must be carried out by a Gas Safe registered engineer.1
Part L and Boiler Plus requirements. The current in-force Approved Document L, Volume 1 (2021 edition incorporating 2023 amendments) sets separate requirements for new and existing dwellings. Wet gas heating systems in both have a 92% ErP minimum, with appropriate time and temperature controls. In an existing dwelling, installing a gas combi also requires one of four additional efficiency measures — flue gas heat recovery, weather compensation, load compensation, or a smart control with automation and optimisation. A new-build dwelling is assessed separately against the applicable new-dwelling Part L requirements, including the whole-dwelling targets and fixed-building-services provisions.2
Building Regulations notification. A new boiler is notifiable building work. Per the Gas Safe Register, the installer notifies (self-certifies) the installation to the local authority within 30 days, and a Building Regulations Compliance Certificate is issued for the property.3 Keep that certificate. If the job includes an unvented hot-water cylinder, it is notifiable G3 work and must be installed and commissioned by a person competent in unvented systems, using either the relevant competent-person self-certification route or Building Control, with the required safety devices under Approved Document G.4 Building Control involvement does not make an otherwise unqualified installer competent to carry out the work.
What the pre-installation survey checks. The installer should calculate heat demand, test mains flow and pressure, confirm gas-pipe capacity, inspect the existing system condition, and plan the flue terminal, condensate discharge, controls and service access. These checks establish whether the work is a genuine like-for-like swap or a relocation that needs additional pipework, building work or permission. If pressure or pipe-sizing checks show the existing gas supply is inadequate, the required upgrade should be agreed before installation and commissioning.
Installation day, commissioning and handover. Heating and hot water are normally unavailable while the old appliance is isolated and the new installation is connected; the installer should explain the expected interruption before work starts. Commissioning includes the required gas-rate and combustion checks, safety-device and control tests, condensate inspection, system filling and venting, and balancing or flow-temperature checks appropriate to the design. The engineer completes the Benchmark record, explains the controls and maintenance requirements, and leaves the Building Regulations and warranty documentation.
A low-carbon alternative to be aware of. As at 16 July 2026, the government’s Boiler Upgrade Scheme, administered by Ofgem, offers £7,500 towards eligible air-to-water, ground-source and water-source heat pumps, £2,500 towards eligible air-to-air heat pumps in residential properties, and £5,000 towards eligible biomass boilers.5 Grant values and eligibility can change, so check Ofgem before deciding.
Hard water, Earlsfield’s stock and new-build SW18
Two local factors shape a good Earlsfield install: the water, and the building.
Select water treatment and protection from the survey. Thames Water confirms that the water in its region is hard.6 The system should be cleaned as required and filled with suitable inhibitor in accordance with the boiler manufacturer’s instructions and BS 7593. A scale reducer, magnetic filter or other protection is selected from the appliance instructions, measured water characteristics and the condition and design of the existing system; those items are not universally mandatory for every installation. The agreed measures and commissioning results should be recorded on the Benchmark checklist.7
The survey decides the boiler and system design. The installer should calculate the heat demand and consider simultaneous hot-water use, available mains flow and pressure, gas-supply capacity, emitter sizes and the existing controls. A flat is not automatically a combi job and a house is not automatically a system-boiler job. A like-for-like swap becomes a relocation when the boiler, flue, condensate or significant pipework moves, which can add building work, access requirements and permissions.
Leasehold, flue and access constraints need resolving before the quote is final. In a leasehold flat, changing a flue terminal through an external wall may require freeholder approval. A rear-extended terrace may restrict the compliant flue route or condensate route. Replacing a cylinder in an upper-floor conversion also requires a delivery route, floor-loading and safe-drainage plan. These are property-specific survey issues; borough-wide housing figures do not establish what system a particular Earlsfield address has.
Safety first
If you smell gas or suspect a leak or carbon monoxide, follow the HSE gas-emergency steps before any work.
1. Don’t switch anything electrical on or off, no naked flames, no smoking — and don’t use a mobile near the suspected leak.
2. Open doors and windows if it’s safe to do so.
3. If the meter control valve is known and safely reachable, turn the gas off at the meter (unless it’s in a cellar).
4. Leave the building if the smell is strong or you feel unwell.
5. Call the National Gas Emergency Service on 0800 111 999 from outside, and don’t go back in until a gas engineer gives the all-clear.
Carbon monoxide. A poorly-running gas appliance can produce CO, and it can come from any faulty combustion appliance. A CO alarm should comply with BS EN 50291 and be sited in line with the manufacturer’s instructions. A new install is a good moment to check the alarm is present and in date.
Gas Safe only, and landlord duties. Only a Gas Safe registered engineer may install a gas boiler; the boiler itself and the final pipework connection must be theirs, per the HSE.1 Landlords: from 1 October 2022 you must provide a CO alarm in any room used as living accommodation with a fixed combustion appliance (excluding gas cookers), per the HSE.9
Find a verified engineer by district
The right install depends on your stock. Coverage varies by listing — confirm yours when you call.
Garratt Lane & the district centre (SW18) — in a flat over a shop, the survey checks cupboard access, gas supply, flue and condensate routes and how the work can be sequenced without obstructing the business below.
Magdalen Road & the terraces north of the railway (SW18) — rear extensions can restrict the flue-terminal position and condensate route. A proposed relocation should be surveyed as building work rather than priced as a simple swap.
Henry Prince, Atheldene & the southern estates (SW18) — in a managed or leasehold flat, confirm who approves changes to external walls, communal fabric and access. The installer still handles the required notification and commissioning records for the individual installation.
Summerstown & the Wandle/Garratt Park side (SW18/SW17) — survey the heat demand, mains performance, gas supply and existing system condition before deciding between repair, like-for-like replacement, conversion or relocation.
New-build and infill along Garratt Lane (SW18) — first-time installations in new dwellings follow the applicable new-dwelling Part L requirements. Later replacements must still be surveyed for the existing flue, condensate, controls and leasehold constraints.
What it costs
Editorial estimate only, observed across independent Gas Safe contractors and directories serving south-west London in early 2026. These are NOT regulated rates, NOT market data and NOT a published cost survey. Earlsfield is inside the London-wide ULEZ and outside the central Congestion Charge zone, so a Earlsfield-based engineer doesn’t carry Congestion Charge overhead — figures are not a substitute for a written quote.
| Job | Typical range |
|---|---|
| Combi swap, like-for-like | £1,800–£3,000 |
| New combi with relocation / system upgrade | £2,500–£4,500+ |
| System boiler + hot-water cylinder install | £3,000–£5,500+ |
| System-to-combi conversion | £3,000–£5,000+ |
| Unvented hot-water cylinder install (G3 notifiable) | £2,000–£4,000+ |
| Flue / condensate re-routing | £150–£600 |
| System filter fitted (where specified) | £150–£300 |
Confirm the quote states the cleaning and inhibitor work, any specified scale protection or system filter, Building Regulations notification and the Benchmark checklist. The protection package should match the manufacturer’s instructions, measured water characteristics and existing system condition.
Why verified engineers — not a general directory
A boiler install is gas work, notifiable building work and a warranty-and-compliance paper trail all in one — so the credential that matters most is Gas Safe registration, checked rather than claimed.
Every listing on this page is checked before it goes live and re-verified annually. We confirm the business is legitimately trading and verify the named contact, we check evidence of public liability insurance, and we confirm Gas Safe registration directly with the Gas Safe Register before a profile is approved — and we confirm the engineer covers Earlsfield’s SW18 (and neighbouring SW17/SW12/SW19/SW11) postcodes. When an engineer attends, ask to see their Gas Safe ID card, and make sure you receive the Building Regulations Compliance Certificate and Benchmark checklist afterwards.
Profiles may be suspended or removed if credentials lapse or credible concerns are raised — see the full verification process →. We’re a pay-to-list directory, not a lead broker: there is no pay-to-play ranking and no per-enquiry middleman fee, and enquiries go directly to the engineer.
Frequently asked questions
Only a Gas Safe registered engineer — the HSE is clear the boiler itself and the final pipework connection must be theirs. Every listing here is checked as registered; still ask to see the ID card.
For an existing dwelling, a wet gas heating system has a 92% ErP minimum with appropriate controls; an installed gas combi also needs one of the four additional efficiency measures. A first installation in a new-build dwelling is assessed separately under the new-dwelling Part L requirements. Ask the installer which provisions apply to the specific project.2
Yes — a new boiler is notifiable, the installer notifies the work through the applicable route, and a Building Regulations Compliance Certificate is issued. Keep it because evidence of compliance is commonly requested during conveyancing. You should also receive the completed Benchmark record and any documents required by the manufacturer’s warranty terms.
Cleaning as required and suitable inhibitor on final fill in accordance with the manufacturer’s instructions and BS 7593. Any scale reducer, magnetic filter or other protection should be selected from the measured water characteristics, appliance requirements and existing system condition, then recorded on the Benchmark checklist.
The survey should decide it from calculated heat demand, simultaneous hot-water use, mains flow and pressure, gas-supply capacity, space, controls and the existing distribution system. Property type alone is not enough. See the combi-vs-system guide below.
It can be. As at 16 July 2026, the Boiler Upgrade Scheme offers £7,500 towards eligible air-to-water, ground-source and water-source heat pumps and £2,500 towards eligible air-to-air heat pumps in residential properties. Suitability depends on the property, insulation, heat demand and available space. Grant values and eligibility can change, so check Ofgem and obtain a proper assessment before deciding.
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Related areas
Verified Gas Safe engineers across Earlsfield’s neighbourhoods, including:
- Atheldene
- Garratt Lane
- Henry Prince Estate
- Magdalen Road
- Southfields (Earlsfield edge)
- Summerstown
- Wandsworth Common (Earlsfield edge)
Related services
Other verified plumbing services in Earlsfield:
Related guides
A good Earlsfield boiler install is Gas Safe, notified for Building Regulations and designed to the applicable Part L requirements. The survey should cover heat demand, mains flow, gas-supply adequacy, flue and condensate routes, access and leasehold permissions. Cleaning, inhibitor and any scale or magnetic protection should match the manufacturer’s instructions and the site assessment. Compliant installation, commissioning and maintenance support reliability and warranty cover, but they do not guarantee a fixed trouble-free lifespan.
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Last reviewed: May 2026 by Adiel Khan — SFEDI-accredited business advisor 20+ years experience (South East Enterprise Ltd) and operator of VerifiedPlumbers. LinkedIn ↗
This page is checked for compliance and regulatory accuracy against the Gas Safety (Installation and Use) Regulations 1998, HSE, Gas Safe Register, GOV.UK Approved Documents L and G, the HHIC Benchmark code of practice, BS 7593, Ofgem and Thames Water. Source links are provided within this page where relevant.
Sources & further reading
1. HSE — Gas safety check: who can do it? (the gas boiler itself and the final pipework connection must be a Gas Safe registered engineer; non-registered persons limited to “wet work”). https://www.hse.gov.uk/gas/landlords/safetycheckswhocan.htm
2. GOV.UK — Approved Document L, Volume 1: Dwellings, 2021 edition incorporating 2023 amendments (separate gas-heating requirements for new and existing dwellings; 92% ErP minimum; additional combi efficiency measure for installations in existing dwellings): https://assets.publishing.service.gov.uk/media/662a2e3e55e1582b6ca7e592/Approved_Document_L__Conservation_of_fuel_and_power__Volume_1_Dwellings__2021_edition_incorporating_2023_amendments.pdf
3. Gas Safe Register — Building Regulations certificates (new heat-producing appliance notified/self-certified to the local authority within 30 days; Building Regulations Compliance Certificate issued). https://www.gassaferegister.co.uk/gas-safety/gas-safety-certificates-records/building-regulations-certificate/
4. GOV.UK — Approved Document G (unvented hot-water storage as notifiable G3 work; competent-person or Building Control route; safety devices). https://assets.publishing.service.gov.uk/media/66f6c6ce3b919067bb4828cc/ADG_with_2024_amendments.pdf
5. Ofgem — Boiler Upgrade Scheme (as at 16 July 2026: £7,500 for eligible air-to-water, ground-source and water-source heat pumps; £2,500 for eligible air-to-air heat pumps in residential properties; £5,000 for eligible biomass boilers; values and eligibility subject to change). https://www.ofgem.gov.uk/environmental-and-social-schemes/boiler-upgrade-scheme-bus
6. Thames Water — Hard water (all water in the Thames Water region is hard). https://www.thameswater.co.uk/help/water-and-waste-help/water-quality/hard-water
7. HHIC — Benchmark Commissioning & Service Record (cleaning and inhibitor in accordance with BS 7593 and the manufacturer’s instructions; records prompts for hard-water conditions and installed protection, without making one protection package universal). https://www.hhic.org.uk/uploads/5D9B41557255E.pdf
8. ONS — How life has changed in Wandsworth: Census 2021 (36.3% private renting). https://www.ons.gov.uk/visualisations/censusareachanges/E09000032/
9. HSE — Gas safety: landlords and letting agents (CO alarm requirement from 1 October 2022). https://www.hse.gov.uk/gas/domestic/faqlandlord.htm</a>