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Gas Safe engineer carrying out boiler repair in a London property
Gas Safe Registered

Boiler Repair London — Gas Safe Engineers

Same-day boiler diagnosis from £95. Worcester Bosch, Vaillant, Ideal, Baxi and Glow-worm specialists. Fixed-price quote before any work — no charge if you decline. BS 6798 and Boiler Plus 2018 compliant.

Landlord CP12 add-on £25–£35. Worcester accredited installer for new boiler quotes from £2,200 supply & fit.

0207 046 1363WhatsApp 07456 975436Book online

24/7 line — averaging 2–4 hour attendance in zones 1–3. Co. No. 17120057.

£5M Public Liability
● Gas Safe Registered
24/7 Same-Day Calls
BS 6798 + Boiler Plus 2018
2–4 hr London Response
Quick Answer

Boiler repair in London costs £95–£480 depending on the fault. Diagnosis is £95–£140 and covers the first 45 minutes. Common repairs: diverter valve £180–£280, expansion vessel £160–£250, pump £180–£320, PCB £280–£480, gas valve £320–£480. A new combi boiler starts at £2,200 supply & fit. Every quote is fixed in writing before work — call 0207 046 1363.

Gas Safe boiler repair across London

A broken boiler in a London winter is not just an inconvenience — under the Landlord and Tenant Act 1985 a landlord is legally required to keep the heating and hot water working, and most home insurance policies require a Gas Safe registered engineer for any repair claim. We attend most central London no-heat calls within 2–4 hours, diagnose the fault inside the first 45 minutes, and confirm a fixed-price quote before any further work. If you decline the repair, you pay only the £95 call-out.

Every visit is by an engineer on the Gas Safe Register — the only legally recognised gas competence body in Great Britain. Cards are shown on arrival and can be verified live on the Gas Safe website. Test equipment is calibrated annually: Anton Sprint combustion analysers, Testo manometers and Fluke multimeters, with calibration certificates kept on the van. We work to BS 6798:2014+A1:2017 for installation and maintenance, BS 5449 for heating system design, BS 7593:2019 for system water quality and Boiler Plus 2018 Building Regulations Part L for every new install.

For boilers beyond economical repair, replacement quotes start at £2,200 for a like-for-like combi swap and £2,600 for a system or conventional swap — all Boiler Plus compliant with smart controls included. Worcester Bosch accredited installers, so you get the full 10-year warranty on Greenstar 4000 and 8000 ranges. Need it today? Call 0207 046 1363.

What our boiler repair covers

Same-day diagnosis

Most calls attended within 2–4 hours. £95 standard call-out includes the first 45 minutes of diagnostic time.

Fixed-price quotes before work

No clock running — you approve the figure first. No charge if you decline the repair.

All major brands stocked

Common PCBs, diverter valves, pumps, expansion vessels and PRVs carried for Worcester, Vaillant, Ideal, Baxi, Glow-worm.

Combi, system and conventional boilers

Closed-vented, vented and unvented systems all serviced. Sealed-system fill loops and F&E tanks.

Gas Safe regulated work

Every engineer holds CCN1, CENWAT, CKR1, HTR1 and MET1 where appropriate. Gas Safe ID on every visit.

Power flushing & system clean

BS 7593:2019 compliant chemical flush or magnetic power flush. Magnacleanse station for problem systems.

Annual service & landlord CP12

Combined service + Gas Safety Certificate from £85 — cheaper than two separate visits.

Boiler replacement quotes

Like-for-like swap from £2,200, system upgrade from £2,600. Worcester Bosch accredited installer.

Building Regs Part L notification

Every new boiler notified to the local authority within 30 days. Gas Safe Building Regs certificate posted to the property.

Warranty registration

Manufacturer warranty registered on the day — 10 years on Worcester Greenstar 4000/8000, 7 years on Vaillant ecoTEC.

Common boiler faults we fix

These are the day-to-day calls — 80% of London boiler faults sit inside this list. Most are diagnosed in the first 45 minutes and fixed the same visit from van stock.

Gas Safe engineer diagnosing a combi boiler fault in London

No heating or hot water

Diverter valve, diaphragm, pump or PCB fault — diagnosed within the first hour.

Boiler keeps switching off (locking out)

Pressure loss, flame-failure detection, fan or APS fault. Common on Worcester Greenstar and Vaillant ecoTEC.

Banging / kettling / whistling noises

Limescale in the heat exchanger or sludge in the system. Often a power flush candidate.

Pilot light keeps going out

Thermocouple, gas valve or flue blockage. Open-flued boilers only — combis use electronic ignition.

Low boiler pressure (below 1.0 bar)

Filling loop leak, PRV failure, expansion vessel waterlogged, or micro-leak on the heating circuit.

Leaking from underneath the boiler

Auto-air vent, pump seal, heat exchanger or PRV discharge. Some leaks fail the boiler immediately under BS 6798.

F-codes / error codes on display

Manufacturer fault codes decoded on the visit — F22, F75, EA, A01 etc all have a specific cause.

Radiators cold at the bottom

Magnetite sludge build-up. Treat with a chemical flush or full BS 7593:2019 power flush.

Hot water lukewarm only

Diverter valve stuck in mid-position, or DHW plate heat exchanger blocked with scale (combi only).

Boiler ignites then cuts out (short cycling)

Often a faulty flow sensor, blocked filter or wrong gas pressure. Combustion analysis required.

Boiler repair cost in London — 2026 prices

Indicative pricing for the most common London boiler repairs. The figure on the day is fixed in writing before work starts — agreed once the engineer has the fault confirmed. Diagnosis covers the first 45 minutes and is non-refundable but credited against any repair you agree to on the visit.

JobTypical CostTime
Boiler fault diagnosis (first hour)£95 – £14045–60 mins
PCB (printed circuit board) replacement£280 – £4801.5 hours
Diverter valve replacement£180 – £2801.5–2 hours
Expansion vessel replacement£160 – £2501.5 hours
Central heating pump replacement£180 – £3202 hours
Gas valve replacement£320 – £4802 hours
Fan / APS (air pressure switch)£220 – £3801.5 hours
Heat exchanger descale / clean£180 – £2602 hours
PRV (pressure relief valve)£120 – £1801 hour
Power flush (up to 10 radiators)£480 – £6804–6 hours
New combi boiler — supply & fitfrom £2,2001 day
New system / conventional boilerfrom £2,6001–2 days

* Prices include VAT and London labour. Full price list on the pricing page. Out-of-hours surcharge applies after 8pm and on Sundays.

Need a fixed price right now?

Phone the line, describe the boiler and fault, get an honest range before anyone leaves the workshop.

Call 0207 046 1363

How a boiler repair visit works

1. Call & describe the fault

5 mins

Phone 0207 046 1363. We ask for the boiler make, model, age and the symptoms — fault code if any. Most faults are correctly predicted on the call so the engineer brings the right part.

2. Engineer attends same day

Within 2–4 hours

Gas Safe ID shown on arrival. £95 standard call-out includes the first 45 minutes of diagnostic time. Combustion analyser, manometer and multimeter used as standard.

3. Fixed-price quote agreed

10 mins

Once the fault is confirmed, a written fixed-price figure is given before any further work. You can accept, decline or get a second opinion — no obligation.

4. Repair carried out

1–3 hours typical

Common parts are fitted from van stock the same visit. Less common parts collected from a London trade counter within the same day where possible.

5. Test, commission, certificate

20 mins

Boiler retested under load, gas rate and flue gas analysis recorded, pressure set to spec. Repair certificate emailed; CP12 issued if combined with a service.

Brands we repair and install

Common parts carried for the brands below. Worcester Bosch and Vaillant ecoTEC represent over 60% of our London call-outs. We are a Worcester Bosch accredited installer so new Greenstar boilers come with the full 10-year manufacturer parts and labour warranty.

Worcester BoschVaillantBaxiIdealGlow-wormPottertonFerroliIntergasViessmannAlphaAristonRemehaMainVokeraBiasiSime

And many more. Not listed? Call 0207 046 1363 to confirm.

Standards, regulations and certification

Every boiler repair and install we carry out in London is referenced to the published standards and regulations below. They are the legal and technical baseline for safe gas work in Great Britain.

Gas Safe engineer test equipment and tools used during a London boiler repair

Gas Safe Register

Every engineer carries a Gas Safe ID card — the only legally recognised register for gas work in Great Britain. Card includes a photo, a registration number and a list of competence categories (CCN1, CENWAT, CKR1, HTR1, MET1). The card can be checked on the Gas Safe website before the engineer starts work.

BS 6798:2014 + A1:2017

The British Standard covering the installation and maintenance of gas-fired boilers up to 70 kW net input. Defines flue position, ventilation, condensate routing, pipework sizing and commissioning procedure. Every new boiler we fit is certified compliant.

BS 5449 (heating systems)

Code of practice for central heating for domestic premises — covers system layout, radiator sizing, pump head, F&E tank requirements and corrosion protection. Older systems pre-dating BS 5449 often need rebalancing and an inhibitor top-up.

BS 7593:2019

Code of practice for preparing, commissioning and maintaining domestic central heating systems. Mandates an in-line magnetic filter (e.g. MagnaClean, Adey) on every new boiler install and a chemical flush before commissioning.

Boiler Plus 2018 (Building Regs Part L)

Statutory rules in force since April 2018: every new combi boiler in England must be ErP A-rated, fitted with time and temperature controls (programmer + room thermostat), plus ONE of: weather compensation, load compensation, smart controls (with auto-on/off and optimisation) or flue gas heat recovery.

Building Regulations Part L1A/L1B

Conservation of fuel and power. Every new or replacement boiler in England must be notified to the local authority within 30 days. Gas Safe handles the notification automatically when the engineer signs off the work on their app.

Building Regulations Part J

Combustion appliances and fuel storage. Covers flue clearances from windows, doors, boundaries and roof terminals. The Plume Management Kit (PMK) extension is often required in London terraced properties where the standard horizontal flue would clip a boundary.

Real London boiler repairs — recent cases

Anonymised worked examples from the last 90 days. Property type, fault, fix, parts, time and cost — all real numbers from the job sheet.

Combi boiler installation in a London property

Victorian terrace, 2-bed flat — Hackney

Worcester Greenstar 30CDi (8 years old), F22 fault code. Pressure had dropped to 0.4 bar repeatedly. Diagnosed waterlogged expansion vessel — the air charge had bled out over time. New 8-litre external vessel fitted in parallel. Cost £180, time 1.5 hours. System repressurised, run for 30 minutes, no further drop.

Edwardian house, 4-bed — Wandsworth

Vaillant ecoTEC Plus 832, intermittent hot water. F.75 fault on cold mornings. Confirmed pump start fault — the impeller was stuck after summer shutdown. New Grundfos UPS pump fitted, system inhibitor topped up. Cost £260 including pump and labour. Boiler restored to full output within 2 hours.

Modern 1-bed flat — Tower Hamlets

Ideal Logic Combi 24, no central heating, hot water OK. Classic diverter valve symptom. Replaced with the brass-bodied service kit (more durable than the original plastic), and the cartridge motor at the same time. Cost £220, time 1.5 hours. New 2-year parts warranty on the kit.

1930s semi, 3-bed — Camden

Baxi Duo-Tec 33 HE (14 years old) — repeat lockouts on the PCB. After three previous repairs the customer chose replacement over another PCB. Worcester Greenstar 30i system boiler fitted with Magnaclean Pro2, new programmer, Wave smart thermostat (Boiler Plus compliant), plus a chemical flush of the system. Cost £2,650 supply and fit, 1 day on site, 10-year Worcester warranty.

Loft conversion combi — Islington

New Vaillant ecoTEC Pro 28 fitted in a loft eaves cupboard. Required a 2 m horizontal flue plus Plume Management Kit to clear the neighbour's window. Building Regs Part J compliant. Hive Active Heating fitted as the load compensation control to meet Boiler Plus. Cost £2,850 supply and fit including PMK and Hive.

End-of-terrace, magnetite sludge — Lewisham

Old Potterton system boiler, radiators cold at the bottom, banging from the pump. Power flushed 9 radiators with Sentinel X400 + X200, fitted a MagnaClean Professional 2 on the return, dosed with X100 inhibitor. Cost £620, time 5 hours. Flow temp restored from 52 °C to 78 °C.

Repair or replace? The honest answer

Most London engineers will quietly default to "replace" because it is the bigger ticket. We give you the maths instead. A modern A-rated condensing combi runs at 92–94% efficiency. A 15-year-old non-condensing boiler runs 65–75%. On a London gas bill that is roughly £200–£400 a year in running costs. Combine that with the failure curve of older PCBs and gas valves and the decision usually makes itself.

  • • Under 8 years old: repair almost always. Spare parts are still made, warranties may still apply.
  • • 8–12 years old: repair if the bill is under 50% of replacement and the boiler is on the current parts list.
  • • 12–15 years old: borderline — depends on the fault. PCB or heat exchanger fault usually tips toward replacement.
  • • Over 15 years old: replacement nearly always wins on running cost alone. New Worcester Greenstar 4000 from £2,200 supply & fit, 10-year warranty.

See our boiler service cost guide for London for the full numbers and the central heating service page if the system needs more than just a boiler swap.

Boiler repair FAQ

How much does boiler repair cost in London?
Boiler repair in London ranges from £95–£480 depending on the fault. The diagnostic call-out is £95–£140 and includes the first 45 minutes on site. Common repairs sit in the middle of that range: a diverter valve is £180–£280, an expansion vessel £160–£250, a central heating pump £180–£320 and a PCB £280–£480. A gas valve is the most expensive common job at £320–£480. Every quote is fixed in writing before work starts — you can decline and pay only the call-out.
Are you Gas Safe registered?
Yes. Every engineer is on the Gas Safe Register — the only legally recognised gas competence register in Great Britain. Cards are presented on arrival and can be verified on the Gas Safe website before any work starts. Categories held include CCN1 (core), CENWAT (central heating and water), CKR1 (cookers), HTR1 (heaters) and MET1 (meters). Working on gas without Gas Safe registration is a criminal offence under the Gas Safety (Installation and Use) Regulations 1998.
What are the most common Worcester Bosch, Vaillant and Ideal faults?
Worcester Greenstar models most often present with the EA fault (ignition / flame loss — typically the electrode kit), the F22 fault (low pressure — usually the expansion vessel) and A01 / D5 hot water faults (diverter actuator). Vaillant ecoTEC commonly show F.22 (low water level), F.75 (pump pressure not detected) and F.28 (no ignition). Ideal Logic and Logic Plus see L2 (ignition lockout), F1 (low pressure) and F2 (flame loss). We stock the common parts for all three brands on the van.
Should I repair or replace my boiler?
As a guide: under 8 years old, repair almost always. 8–12 years old, repair if the bill is under 50% of replacement and the boiler is on the current spare-parts list. Over 12 years old or off the parts list, replacement usually wins on running cost alone — a new A-rated condensing combi runs 92–94% efficient against 65–75% on an old non-condensing unit. We give you both numbers on site so you decide on facts, not pressure. Replacement quotes start from £2,200 for a like-for-like combi, £2,600 for a system or conventional swap.
How long does a boiler repair take?
Most repairs are completed within 1–3 hours on the first visit. Simple part swaps like a diverter cartridge, PRV or auto-air vent are under an hour. Pump or expansion vessel replacements run 1.5–2 hours. PCB and gas valve replacements typically take 2 hours including commissioning and combustion analysis. Boilers needing parts ordered to manufacturer spec are rare in London — we collect from Plumb Center, Williams or City Plumbing the same day where stock allows.
Do I need an annual boiler service?
Yes for two reasons. First, the manufacturer warranty (typically 7–10 years on Worcester, Vaillant, Ideal and Baxi) is only valid if the boiler is serviced once a year by a Gas Safe engineer — proven by a stamped service record or digital benchmark. Second, BS 6798 and most home and landlord insurance policies require annual servicing for safety. A service costs £85–£110 standalone, £85 combined with a CP12 Gas Safety Certificate for landlords.
What is Boiler Plus 2018 and does it affect me?
Boiler Plus is a 2018 amendment to Building Regulations Part L that applies to every new or replacement combi boiler in England. The boiler must be ErP A-rated (≥92% efficiency), and the install must include time and temperature controls (programmer + room thermostat), plus ONE additional energy-saving measure: weather compensation, load compensation, smart controls with auto-on/off and optimisation (e.g. Hive, Nest, Tado, Worcester Wave) or flue gas heat recovery. We quote a Boiler Plus compliant package every time — usually with smart controls as the easiest and most useful add-on.
What does the £95 call-out cover?
The £95 standard call-out covers travel within the London area, attendance on site by a Gas Safe engineer and the first 45 minutes of diagnostic work — long enough to confirm 80% of common faults. If the repair runs over 45 minutes the time is charged at our published hourly rate, agreed and fixed in writing before continuing. If you decide not to proceed with the repair after diagnosis, you pay only the £95 call-out and nothing more.
Do you carry parts for all boiler brands?
Yes. Van stock covers the high-demand parts for Worcester Bosch (Greenstar 25Si, 30CDi, 4000/8000), Vaillant (ecoTEC Plus and Pro), Ideal (Logic, Logic Plus, Vogue), Baxi (Platinum, Duo-Tec), Glow-worm (Energy, Ultimate) and Potterton. That covers around 85% of combi repairs in London. Less common parts — Viessmann, Intergas, Remeha — are collected from a London trade counter the same day where possible. Pricing is the same whether the part comes from van or trade counter.
How quickly can you attend an emergency no-heat call?
Most no-heat calls in central and inner London (zones 1–3) are attended within 2–4 hours. Outer London (zones 4–6) typically 3–6 hours. Out-of-hours, weekend and bank holiday calls carry a small uplift but are still attended same-day in over 95% of cases. The phone line (0207 046 1363) is answered 24/7 — if all engineers are committed at the time of your call we will give an honest ETA rather than book a slot we cannot keep.
Will I get a certificate after the repair?
Yes. A repair report is emailed within 24 hours listing the fault diagnosed, the part fitted, the gas rate measured (mbar working pressure), the flue gas analysis (CO/CO₂ ratio) and any system pressure or balancing notes. If the visit was combined with a service or CP12, a Gas Safety Record (Landlord CP12) is issued at the same time. Both documents are PDF-signed and stored on our system for 6 years for compliance audits.
Can you replace the boiler the same day?
For a like-for-like combi swap in the same position, yes — typical timeline is 7am to 4pm on a single day. For a relocation, system conversion (e.g. conventional to combi), or where new gas pipework, condensate routing or a flue route through a chimney is needed, the work runs 1.5–2 days. A free survey is offered before the install date so the second day is planned, not a surprise. Replacement quotes start from £2,200 for a combi, £2,600 for a system boiler.
Do you cover landlord and commercial boiler repair?
Yes. Landlord boiler repair includes a CP12 Gas Safety Certificate on the same visit at no extra labour — only the certificate fee (£25–£35 depending on number of appliances). For managed portfolios we run PPM (Planned Preventative Maintenance) contracts with anniversary-keyed reminders for CP12, EICR, FRA and PAT. Commercial boilers up to 70 kW net are covered as standard; over 70 kW falls under Commercial Gas (COCN1) — we have engineers on both registers.
What if you cannot fix the boiler?
If the fault cannot be diagnosed or repaired on the first visit you pay only the £95 call-out, no labour. We never invoice for guesswork. Where the boiler is beyond economical repair (obsolete parts, cracked heat exchanger, multiple system failures) a replacement quote is provided on the spot with options for combi, system and conventional swap. If you choose to replace within 14 days the £95 diagnostic fee is credited against the new boiler quote.
Are you insured?
Yes. We carry £5 million public liability insurance covering domestic, commercial and landlord work. £2 million employers' liability. £250,000 professional indemnity covering design errors on heating system installs. Certificates of insurance can be emailed in advance for property managers, landlords and freeholder boards before site attendance. London 247 Home Services Ltd, Co. No. 17120057.

Still got questions? Call our 24/7 line on 0207 046 1363 or WhatsApp 07456 975436.

Book a Gas Safe engineer today

Same-day London attendance, fixed-price quote before work, no charge if you decline. £95 diagnostic credited against any repair you accept on the visit. Combined boiler service + landlord CP12 available on the same call-out at a discounted rate.

0207 046 1363WhatsApp 07456 975436Book online

Fully insured • Gas Safe Register on every visit • VAT-registered invoices • Manufacturer-backed parts warranty

Service area

Service Area — All London Boroughs

Gas Safe boiler repair attended across Greater London. Central and inner London zones 1–3 within 2–4 hours; outer London 3–6 hours. Out-of-hours and weekend attendance available on the same 24/7 line — 0207 046 1363.

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Gas Safe boiler repair, today.

Diagnosis from £95. Fixed-price quote before any work. No charge if you decline. 24/7 London line.

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