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A boiler repair is a legal Gas Safe job, not a DIY fix. And in Catford, who does it depends on how you hold your home: SE6 council tenants go to the council’s contractor, homeowners call their own Gas Safe engineer — and a gas smell is never a plumber call.
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Smell gas? Call the National Gas Emergency Service on 0800 111 999 first — that’s never a plumber job. Boiler repair itself is a Gas Safe engineer’s work.
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On this page
Why it must be a Gas Safe engineer · Common boiler faults · Catford homes and access · Who repairs it in Catford, by tenure · A gas smell is not a plumber call · Hard water and your boiler · Repair or replace? · What it costs in Catford — 2026 · Why verified engineers · FAQ
Why it must be a Gas Safe engineer
Boiler repair is gas work, and gas work is legally restricted. The HSE is unambiguous: anyone employed to work on gas appliances in domestic premises must be Gas Safe registered and competent in that area of gas work¹, and you can confirm an engineer with the Check an Engineer service by entering their licence number to see their photo and the categories they’re qualified for. An engineer’s ID card should show the specific work they can do — a boiler ticket isn’t the same as a cooker ticket. A cheap “repair” by an unregistered fitter isn’t a bargain; it’s illegal, can invalidate your insurance and warranty, and risks carbon monoxide.
Common boiler faults
Most boiler call-outs are one of a familiar set: no heat or hot water (often a diverter valve, pump, thermostat or a lost-pressure lockout), a boiler that fires then cuts out (a sensor, fan or flue issue), a dropping pressure gauge (a leak or a failed expansion vessel), an ignition or flame-sensing fault, or a fault code that points the engineer straight to the part. Kettling — a rumbling like a boiling kettle — usually means limescale or sludge on the heat exchanger, which in Catford’s hard-water area is common. A good engineer reads the code, checks the obvious cheap causes before the expensive ones, and tells you what the part will cost before fitting it.
Catford homes, access and what the engineer checks
Catford’s housing shapes a boiler repair as much as the fault does. In a converted flat, the boiler is often in a cupboard with a concealed flue and tight access — and an engineer can’t safely complete or sign off work if the required inspection hatches or flue access aren’t reachable, so clearing access before the visit avoids a wasted call-out. Condensate pipes in flats and older terraces often run to awkward external points that can freeze in winter and lock the boiler out. In a newer flat or block there may be no individual boiler at all: heating can come from communal or district plant, sometimes through a heat interface unit, in which case a heat or hot-water fault is the managing agent’s or heat-network operator’s responsibility, not a private engineer’s — so check what serves your home before you book. In older Catford terraces, hard water and system sludge in ageing radiators and pipework sit behind a lot of recurring lockouts and kettling, which is as much a system-cleaning job as a boiler one.
On the appliance itself, a good engineer works through the cheap and obvious before the expensive: the fault code, the system pressure, whether the thermostat and programmer are actually calling for heat, the condensate pipe (a frozen one is a common winter lockout), the expansion vessel and the relief-valve pipe, any visible leaks, and the flue and combustion safety. It’s worth knowing the line, too: radiators, valves and heating pipework can be a competent plumber’s work, but the boiler casing, the gas train, the flue and combustion are strictly Gas Safe.
Who repairs it in Catford, by tenure
This is where Catford differs, and it’s worth getting right before you call anyone.
Council tenants report to Lewisham, not a private engineer. For gas central heating and hot-water servicing and repairs, Lewisham splits the borough by postcode — and for SE6 (Catford), the contractor is BSW: the council’s instruction is to call BSW on 0800 090 2360 or 020 8763 3966, or use the My BSW online portal for non-urgent breakdowns and servicing². General repairs and emergencies go through the council’s main line, 0800 028 2028, which runs an emergency service 24/7³.
Private tenants report a faulty or broken boiler to the landlord or agent first. Your landlord has a legal duty: Lewisham states it is illegal for a landlord not to get a gas safety certificate every year, and if they don’t fix a fault you can contact the council’s Environmental Health team or the HSE Gas Safety Advice Line on 0800 300 363⁴.
Homeowners and leaseholders call their own Gas Safe registered engineer directly — which is where this directory comes in.
A gas smell is not a plumber call
If you smell gas or suspect a leak, stop and call the emergency line first. Lewisham’s own guidance for its tenants is to contact the National Gas Emergency Helpline immediately on 0800 111 999⁵, and National Gas advises opening doors and windows and moving to fresh air⁶. Boiler repair by an engineer comes only after any gas emergency is made safe.
Hard water and your boiler
Catford is in Thames Water’s supply area, and Thames Water is clear that all the water in its region is hard because it passes through chalky limestone⁷. Scale on a boiler’s heat exchanger reduces efficiency and causes the kettling rumble; sludge (from system corrosion) does similar damage and blocks flow. A repair that keeps recurring — noisy operation, intermittent lockouts — is often really a water-treatment problem, fixed by cleaning the system, dosing inhibitor and fitting a magnetic filter rather than swapping part after part.
Repair or replace?
Not every fault is worth repairing. A one-off part on an otherwise healthy boiler is usually worth fixing; but repeated breakdowns, an obsolete or inefficient model, or a major component (heat exchanger, or several parts at once) on an ageing boiler can tip the balance towards replacement. A good engineer will tell you honestly which side of that line you’re on rather than selling you a new boiler by default. Our boiler repair or replace guide walks through the decision.
What boiler repair costs in Catford — 2026
Editorial estimate only — not official pricing, and no substitute for a written quote. Parts vary by make; all boiler/gas work must be by a Gas Safe registered engineer.
| Repair | Typical range |
|---|---|
| Diagnostic call-out / fault-find | £70–£120 |
| Replace sensor / thermocouple / ignition part | £120–£250 |
| Replace diverter valve | £250–£450 |
| Replace circulating pump | £180–£350 |
| Replace PCB (control board) | £250–£500+ |
| Re-pressurise / replace expansion vessel | £120–£350 |
| Fix pressure / fill-loop fault | £90–£200 |
| Descale / clear hard-water blockage | £120–£300 |
| Diagnose intermittent lockout | £90–£200 |
Get the fault diagnosed and the part price confirmed before work starts, and weigh the repair against the boiler’s age.
Why verified engineers in Catford
A boiler is safety-critical, and the wrong person is a real risk. Every engineer listed here is checked before they appear — identity, insurance, trading presence and Gas Safe registration where gas work is involved — and re-checked annually. A flat monthly listing fee means no customer-side fee and no pay-to-play ranking. Always still confirm current Gas Safe registration on the day and that the engineer holds the right category for your boiler; listing checks are administrative and don’t replace your own checks or guarantee workmanship. See how we verify plumbers.
Frequently asked questions
Lewisham, not a private engineer. For SE6, gas heating and hot-water repairs go to the council’s contractor BSW on 0800 090 2360 or 020 8763 3966; general and emergency repairs are on 0800 028 2028, 24/7.
No. Boiler and gas work must be done by a Gas Safe registered engineer competent in that area — check their ID card and verify it with the Check an Engineer service. A plumber without gas registration can’t legally touch the boiler.
It means water is escaping, either a leak or a failed expansion vessel forcing pressure out through the relief valve. Repeated topping-up accelerates corrosion, so it’s worth diagnosing rather than living with.
Your landlord must hold a valid annual gas safety certificate (it’s illegal not to) and deal with a faulty appliance. If they don’t, contact Lewisham’s Environmental Health team or the HSE Gas Safety Advice Line on 0800 300 363.
Usually limescale or sludge on the heat exchanger — common in Catford’s hard-water area. It’s typically solved by cleaning and water treatment, not necessarily a new boiler.
A single part on a healthy boiler is usually worth repairing; repeated faults or a major component on an ageing, inefficient model often favours replacement. A good engineer gives you the honest comparison.
Boiler repair across Lewisham — areas we cover
Boiler Repair Catford · Lewisham · Forest Hill · Hither Green · Bellingham · Sydenham · Ladywell
Related services in Catford
Central Heating Repair · Boiler Installation · Boiler Servicing · Emergency Plumber
Related guides
Boiler Repair or Replace · Boiler Fault Codes · Combi vs System Boiler · London Hard Water Guide · London Plumbing Costs Guide
Source provenance
Guidance on this page is drawn from primary UK sources: the HSE (Gas Safe registration requirement and the Check an Engineer service), the London Borough of Lewisham (SE6 council gas/heating routing to BSW; the 24/7 council repairs line; the gas-leak emergency number for tenants; and private-rented landlord gas-safety duties with the HSE advice line), the National Gas Emergency Service (the emergency number and gas-leak advice), and Thames Water (hard-water region). Cost figures are an editorial estimate only, and repair-or-replace guidance is general, not appliance-specific advice.
Sources & further reading
¹ HSE — Check an engineer (Gas Safe register): https://www.hse.gov.uk/gas/gas-safe-register-check.htm
² Lewisham — Gas servicing and repairs: https://lewisham.gov.uk/myservices/housing/council-tenants/repairs/gas-servicing-and-repairs
³ Lewisham — Request a repair: https://lewisham.gov.uk/myservices/housing/council-tenants/repairs/request-a-repair
⁴ Lewisham — Gas and electrical safety (private tenants): https://lewisham.gov.uk/myservices/housing/private-tenants-and-landlords/advice-private-tenants/your-landlord-s-responsibilities/gas-and-electrical-safety
⁵ Lewisham — Repairs responsibilities (gas emergency): https://lewisham.gov.uk/myservices/housing/council-tenants/repairs/repairs-responsibilities
⁶ National Gas — Emergency contacts: https://www.nationalgas.com/emergency-contacts
⁷ Thames Water — Hard water: https://www.thameswater.co.uk/help/water-and-waste-help/water-quality/hard-water
Last reviewed: July 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 HSE, Gas Safe Register, Lewisham Council, SGN and Thames Water guidance. Source links are provided within the page where relevant.