Heating emergencies — what to do
If you smell gas, don't use any electrical switches, don't light a flame, turn off the gas supply at the meter if it's safe to reach, and call the National Gas Emergency Service on 0800 111 999 before calling a heating engineer. For no heat or hot water without a gas smell, check the boiler pressure and any error code before assuming a full breakdown.
Three steps to hiring the right heating engineer
First, confirm Gas Safe registration and ask to see the ID card, which lists exactly what gas work they're qualified for. Second, get a written quote naming the boiler model. Third, ask what the manufacturer's warranty requires (usually an annual service) to keep it valid.
What is a powerflush and do you need one?
A powerflush clears sludge and debris from radiators and pipework using a pumped chemical flush — often recommended if radiators are cold at the bottom or the system is noisy, and standard practice before fitting a new boiler onto an older system so it isn't immediately clogged.
Oil-fired boilers, what's different
Oil boilers are common in properties off the mains gas network, need an oil storage tank with its own maintenance and safety considerations, and are serviced by OFTEC-registered engineers rather than Gas Safe (which only covers gas). If you're off-grid, confirm your engineer's OFTEC registration specifically.
Why some radiators run cold
A radiator cold at the top usually means trapped air (fixed by bleeding); cold at the bottom usually means sludge build-up (may need a powerflush). A radiator that's cold all over while others work fine often points to a closed valve or a balancing issue across the whole system, not a fault with that radiator itself.
Heating in older and period properties
Older properties often have narrower pipework, no cavity wall insulation, and sometimes a heating system not originally designed for full central heating throughout — all of which affect boiler sizing and radiator choice. A heating engineer working on a period property will usually assess the whole system, not just swap the boiler in isolation.
What affects the cost
Cost depends on the type of system (combi vs system vs conventional), whether it's a straightforward swap or a full system change, boiler brand and output size, and property access. Moving a boiler's location, rather than replacing it in place, adds cost because of the extra pipework, flue routing and making good involved.
First fix and second fix heating work
On a new build or extension, "first fix" is running pipework to radiator and boiler positions before walls are closed up; "second fix" is fitting radiators, thermostats and the boiler itself once decorating is done. Getting boiler flue routing agreed early avoids conflicts with other trades later.