A yearly service keeps a boiler running safely and efficiently — and for a rented home, the law adds a separate annual gas safety check on top. A Gas Safe registered engineer does both. Find a verified one across the Square Mile, and know the gas-safety basics first.

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⚠️ Smell gas? Don’t touch electrical switches or use a naked flame; open doors and windows; from outside call National Gas on 0800 111 999 (24h). Suspect carbon monoxide? Switch the appliance off, get everyone out, call the same number and seek medical help. More in Safety first.

Contact verified Gas Safe boiler engineers in the City of London ↓

Coverage: EC1–EC4, E1 and the WC2A edge — the whole Square Mile, from Temple to the Tower fringe.
What this covers: annual boiler servicing and the landlord’s annual gas safety check (CP12 / Gas Safety Record) — combustion and flue checks, gas pressure, controls and safety devices, plus the legal record a rented home needs.
Something else? A boiler that’s broken down or faulty is boiler repair; a new boiler is boiler installation; radiators, the pump and the wider system are central heating repair.
Costs: usually a fixed price for a service, or a service plus safety check — see what it costs.
Availability: plumbers set their own hours; check each listing for the cover they offer.

Jump to: Service vs safety check · Servicing in the City · Safety first · By district · Costs · FAQs

What a service covers — and how it differs from a gas safety check

These two get mixed up constantly, so it’s worth being clear: they’re different jobs, and one doesn’t do the other’s work.

The annual service is maintenance. A Gas Safe engineer inspects and tests the boiler to the manufacturer’s instructions — combustion and flue, gas pressure and flow, the casing seals, the electrical connections, the controls and safety devices — and cleans components as needed, so the boiler keeps running safely and efficiently. Manufacturers usually specify servicing intervals (commonly annual), and keeping to them is often a condition of the warranty. A flue forms part of the check, and the Gas Safe Register notes the engineer must be able to examine the flue along its length, so a concealed or boxed-in flue may need inspection hatches.³⁶

The annual gas safety check is a legal duty for landlords. The HSE requires a landlord to have an annual gas safety check carried out every 12 months by a Gas Safe registered engineer on the gas appliances and flues they provide, keep the record for two years, and give each tenant a copy within 28 days (and any new tenant a copy before they move in).³⁸ That record is the Gas Safety Record, still widely called a CP12. It confirms the appliances are safe on the day of the check. Installation pipework isn’t part of the annual check itself — it has to be kept in a safe condition as a separate maintenance duty, and the HSE recommends asking the engineer to test the whole gas system for soundness and visually examine the pipework when the safety check is done.³⁹

Why the difference matters. The HSE treats the annual gas safety check and ongoing maintenance as separate duties — a service shouldn’t be assumed to satisfy the safety-check requirement, and a safety check on its own isn’t a substitute for proper maintenance.³⁸ In practice many engineers carry out both in one visit, but they’re recorded as two things. For an owner-occupier a service isn’t itself a legal requirement, but it’s how you keep the boiler safe, efficient and in warranty.

If something’s wrong. A service or check is also when problems surface. If the engineer finds the boiler unsafe, they may leave it isolated, disconnected or capped — with your permission — until it’s put right, and that point is boiler repair, not servicing. A service doesn’t replace a repair where there’s already an active fault, leak or lockout.

Boiler servicing in City flats: access, communal heat and hard water

Boiler servicing in the City is often a flats, managed-block and mixed-use building job — the City of London Corporation counts around 8,600 residents against 678,000 workers in 1.12 square miles¹ — and that shapes the visit.

You may have no gas boiler to service. Some City homes have none: Barbican flats use electric underfloor heating,⁴ and buildings on the Citigen heat network often run via a heat-interface unit in the flat rather than an individual boiler⁶ — an HIU is maintained differently from a gas boiler, often by the building or the network operator. A flat with a heat meter, an HIU cupboard, no individual flue terminal or no individual gas meter may have no gas boiler to service at all.

Access in a managed block. A service is a planned visit, so in a managed building it’s worth arranging concierge or building-management access in advance. The boiler, its casing, the flue route and terminal, and any inspection hatches all need to be accessible on the day — which matters where the boiler sits in a cupboard or the flue terminal is on a shared façade.

Hard water and scale. Thames Water says all the water in its region is hard, so scale builds up over time.⁷ A regular service is a chance to keep an eye on scale, sludge and the system protection (a filter and inhibitor) — but flushing out sludge or wider system treatment is central heating repair, not part of an ordinary service.

If you rent from the City of London Corporation, the Corporation as landlord arranges the annual gas safety check on the gas appliances and flues it provides, and maintains the pipework — report a problem on its repairs line, 0800 035 0003: the Corporation maintains communal areas and its own fittings inside the home, while tenants stay responsible for their own fittings or improvements, and work it isn’t obliged to do can be recharged.¹¹

Safety first

A boiler runs on gas, so a few things matter more than the service itself.

If you smell gas or suspect a leak. Don’t turn any electrical switches on or off, don’t use naked flames or smoke, open doors and windows to ventilate, and turn the gas off at the meter control if you can reach it safely. If the smell is strong, leave the building — then call the National Gas Emergency Service on 0800 111 999 from outside. The line is open 24 hours.¹⁷

Carbon monoxide. CO is a colourless, odourless, tasteless gas that the HSE warns can be produced by any fuel-burning appliance, including a faulty or poorly maintained boiler — which is part of why regular servicing matters.¹⁹ National Gas lists symptoms to watch for — headaches, dizziness, nausea, breathlessness, light-headedness and drowsiness — and warning signs on the appliance itself: sooty marks or staining, a lazy yellow or orange flame instead of crisp blue, and a pilot light that keeps blowing out.¹⁷ If you suspect CO, switch the appliance off, open doors and windows, get everyone out, and from outside call National Gas on 0800 111 999 — then seek immediate medical help, because going out into fresh air won’t treat CO exposure on its own. Don’t go back in until it’s confirmed safe.¹⁷ Fit an audible CO alarm.

Who can service it. A gas boiler service must, by law, be carried out by a Gas Safe registered engineer — never a general handyman.¹⁵ That covers the gas-carrying parts, combustion, flue and the boiler’s sealed casing. The Gas Safe Register notes a purely non-gas component — say a water circulating pump or a control valve within the casing — can be handled by another competent tradesperson where no combustion-chamber seal is broken and no gas-carrying or combustion-controlling part is disturbed,³⁵ but a service itself is Gas Safe work. For an oil or solid-fuel appliance, use a technician competent for that fuel.

The HSE advice line is not an emergency number. The HSE Gas Safety Advice Line, 0800 300 363, is for non-emergency gas safety information during office hours only (Monday to Friday) — it is not a substitute for the 24-hour National Gas emergency line.²¹

Find a verified Gas Safe boiler engineer by district

For a service, the City question is usually access — and whether there’s a gas boiler at all.

Barbican & Golden Lane — estate flats on electric underfloor heating or communal heat may have no gas boiler to service, so confirm the heating type first.

Smithfield & the Farringdon edge — converted and mixed-use flats where a cupboard-mounted boiler and its flue need to be accessible for the service.

Bank, Cornhill, Lombard Street & Mansion House — apartments above the offices where a planned service visit may need concierge or building-management access to the flat, riser or flue terminal.

Liverpool Street, Broadgate & Bishopsgate — modern blocks often on a communal heat network with heat-interface units, maintained differently from an individual gas boiler.

Leadenhall, Fenchurch Street & Gracechurch Street — flats above commercial units where access timing and the flue route shape the visit.

St Paul’s, Cheapside & Paternoster Square — flats where a kitchen-mounted combi behind an access panel is serviced in place, with flue clearances checked.

Cannon Street, Queen Victoria Street & the riverside — compact flats where the service is a good moment to check the condensate route before winter.

Portsoken & the Aldgate edge — the Middlesex Street and Mansell Street estates, where landlord and managed-block arrangements often drive the annual gas safety check.

What it costs

A service is usually a fixed price; a service plus a gas safety check, or a landlord record covering several appliances, costs a little more. The ranges below are a rough sense-check, not a quote.

A weekday Square Mile visit can also carry the Congestion Charge of £18 a day and, for a non-compliant vehicle, the ULEZ charge of £12.50, depending on the vehicle, timing and route.¹³¹⁴ For how to read a quote, see How to Read a Plumbing Quote.

Editorial estimate only — illustrative ranges to help you sense-check a quote. They are NOT regulated rates, NOT market data, and NOT a published cost survey. Always agree the price and what’s included before work starts.

Frequently asked questions

Why verified plumbers — not a general directory

A service and a gas safety check are gas work, so the single most important check is Gas Safe registration — which is exactly what we confirm before a profile goes live.

Every listing is checked before it goes live and re-verified each year: we confirm the business is legitimately trading and verify the named contact, we check evidence of public liability insurance, and we confirm the plumber covers the City’s EC and edge postcodes before a profile is approved. For boiler and gas work, we confirm the engineer’s registration directly with the Gas Safe Register, and you can check any engineer there yourself. For work on the water supply, you can also look a plumber up on WaterSafe.

Profiles may be suspended or removed if credentials lapse or credible concerns are raised — see the full verification process →. No customer middleman fee: enquiries go directly to the plumber.

Related areas

Verified Gas Safe boiler engineers across the City of London’s neighbourhoods, including:

• Bank
• Barbican
• Billingsgate
• Bishopsgate
• Botolph Lane
• Broadgate
• Cannon Street
• Carter Lane
• Cheapside
• Cornhill
• Fenchurch Street
• Fleet Street
• Golden Lane
• Gracechurch Street
• Guildhall
• Leadenhall
• Liverpool Street
• Lombard Street
• Mansell Street
• Mansion House
• Middlesex Street
• Monument
• Moorgate
• Old Bailey
• Paternoster Square
• Portsoken
• Queenhithe
• Smithfield
• St Paul’s
• Walbrook

Related services

Other verified plumbing services in the City of London:

• Emergency Plumber in the City of London
• Burst Pipes in the City of London
• Leak Detection in the City of London
• Blocked Drains in the City of London
• Toilet Repairs in the City of London
• Tap Repair & Installation in the City of London
• General Plumbing in the City of London
• Bathroom Plumbing in the City of London
• Kitchen Plumbing in the City of London
• Washing Machine & Dishwasher Installation in the City of London
• Boiler Repair in the City of London
• Boiler Installation in the City of London
• Central Heating Repair in the City of London
• Commercial Plumbing in the City of London

Related guides

• Boiler Repair or Replace? — A London Guide 2026
• Landlord Plumbing Compliance Checklist — London 2026
• London Plumbing Costs & Compliance Guide 2026

A service keeps a boiler safe and efficient; for a rented home, the annual gas safety check is a separate legal must. Start with a verified Gas Safe engineer who can do both — and if you ever smell gas, it’s National Gas on 0800 111 999 first.

Contact verified Gas Safe boiler engineers in the City of London ↑

← Back to all plumbing services in the City of London

Last reviewed: June 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 bodies cited on this page, including the Gas Safe Register, the HSE, National Gas, Thames Water, the City of London Corporation and Transport for London. Source links are provided within this page where relevant.

Sources & further reading

1. City of London Corporation — Our role in London (residents, workers, area) — https://www.cityoflondon.gov.uk/about-us/about-the-city-of-london-corporation/our-role-in-london
2. City of London Corporation — Barbican Estate repairs and maintenance (electric underfloor heating) — https://www.cityoflondon.gov.uk/services/barbican-estate/barbican-estate-resident-information-pack/barbican-estate-repairs-and-maintenance
3. E.ON — Citigen heat network (how heat networks work) — https://news.eonenergy.com/news/how-heat-networks-work-inside-londons-citigen-energy-network
4. Thames Water — Hard water (regional hardness; limescale) — https://www.thameswater.co.uk/help/water-and-waste-help/water-quality/hard-water
5. City of London Corporation — Report a repair, City of London estates (repairs line; landlord/tenant responsibility; annual gas safety check; rechargeable repairs) — https://www.cityoflondon.gov.uk/services/housing-and-homelessness/housing-services/report-a-repair-city-of-london-estates
6. Transport for London — Congestion Charge — https://tfl.gov.uk/modes/driving/congestion-charge/congestion-charge-zone
7. Transport for London — Ultra Low Emission Zone (ULEZ) — https://tfl.gov.uk/modes/driving/ultra-low-emission-zone
8. Gas Safe Register — official register of gas engineers (gas work must be done by a registered engineer) — https://www.gassaferegister.co.uk/
9. National Gas — Emergency contacts (gas-smell steps; carbon monoxide procedure and symptoms; faulty-boiler signs; 0800 111 999) — https://www.nationalgas.com/emergency-contacts
10. HSE — Carbon monoxide (colourless, odourless, tasteless; any combustion appliance) — https://www.hse.gov.uk/gas/domestic/co.htm
11. HSE — Gas safety contacts (Gas Safety Advice Line 0800 300 363, office hours, non-emergency information only) — https://www.hse.gov.uk/gas/domestic/contacts.htm
12. Gas Safe Register — Home gas safety / who can work on a gas appliance (non-gas component nuance) — https://www.gassaferegister.co.uk/gas-safety/home-gas-safety/home-improvements/
13. Gas Safe Register — Flues in voids FAQs (engineer must be able to examine the flue; inspection hatches for concealed flues) — https://www.gassaferegister.co.uk/gas-safety/home-gas-safety/check-your-gas-appliances/flues-in-voids-faqs/
14. HSE — Gas safety: landlords and letting agents (annual gas safety check every 12 months on appliances and flues; record kept 2 years; copy to tenant within 28 days; maintenance a separate duty) — https://www.hse.gov.uk/gas/domestic/faqlandlord.htm
15. HSE — Maintenance: gas pipework (installation pipework not covered by the annual gas safety check; recommends whole-system soundness test and visual pipework examination when a check is requested) — https://www.hse.gov.uk/gas/landlords/gaspipework.htm