Gas Safe Engineer — What They Can Do (And What They Can't)
Understanding what a Gas Safe engineer can and cannot legally do in London. The difference between a plumber, a Gas Safe engineer and a heating engineer — and why it matters for your property.
What Is a Gas Safe Engineer?
A Gas Safe engineer is a tradesperson registered with the Gas Safe Register — the UK's official list of businesses legally permitted to work on gas appliances and installations. Registration is a legal requirement under the Gas Safety (Installation and Use) Regulations 1998. Anyone working on gas without Gas Safe registration is committing a criminal offence and the work is illegal.
What a Gas Safe Engineer Can Do
- Install, service and repair gas boilers (combi, system and heat-only)
- Install, service and repair gas fires, gas cookers and gas hobs
- Carry out annual gas safety inspections and issue Gas Safety Certificates (CP12)
- Work on gas pipework — fitting new gas supply pipes, tee-ing off for new appliances
- Commission new gas appliances after installation
- Test gas tightness of pipework
- Issue Gas Safety Warning Notices for unsafe installations
- Work on LPG (liquefied petroleum gas) appliances if their card shows LPG registration
What a Gas Safe Engineer Cannot Do Without Additional Qualifications
- Electrical work: Wiring a new programmer, replacing a fused spur, or installing a new thermostat circuit requires Part P electrical qualification unless the gas engineer also holds electrical qualifications.
- Unvented hot water cylinders: Working on unvented (pressurised) hot water systems requires a separate G3 qualification.
- Oil boilers: Oil heating systems require OFTEC registration, not Gas Safe registration.
- Refrigerants: Air conditioning and heat pump refrigerant work requires F-Gas certification.
Gas Safe Engineer vs Plumber: What Is the Difference?
A plumber works on water systems — cold water supply, hot water distribution, drainage, and sanitary ware. A Gas Safe engineer works on gas systems. Many gas engineers are also qualified plumbers (particularly heating engineers), but the two skills are distinct and the qualifications are separate.
For a boiler replacement in London, you need someone who is both — a heating engineer who is Gas Safe registered, can disconnect the old boiler and connect the new one to the gas supply, and can also work on the central heating pipework and primary circuit.
How to Check Gas Safe Registration
Every Gas Safe registered engineer carries a Gas Safe ID card. Check:
- The card has not expired (check the expiry date on the back)
- The engineer's photo matches the person at your door
- The card lists the type of work they are registered for (natural gas, LPG, central heating, etc.)
You can also verify registration online at gassaferegister.co.uk using the engineer's registration number.
Frequently asked questions
Do I need a Gas Safe engineer to service my boiler?
Yes. All boiler service work — including annual servicing and gas safety certificates — must be carried out by a Gas Safe registered engineer. Using an unregistered person to work on gas appliances is illegal and dangerous.
What is the difference between a Gas Safe engineer and a plumber?
A plumber works on water systems (pipework, drainage, hot water cylinders). A Gas Safe engineer is qualified and legally authorised to work on gas appliances. Many heating engineers hold both qualifications. For boiler work, you need a Gas Safe registered heating engineer.
Can I check if someone is Gas Safe registered?
Yes — visit gassaferegister.co.uk or call 0800 408 5500. You can search by the engineer's name, business name or registration number. Always ask to see the Gas Safe ID card before allowing any gas work to begin.
Is it illegal to work on gas without Gas Safe registration?
Yes. Working on gas appliances without Gas Safe registration is a criminal offence under the Gas Safety (Installation and Use) Regulations 1998. It also invalidates home insurance and can result in prosecution if the work causes harm.