Boiler servicing
An annual service is the cheapest thing you can do for a heating system. It keeps a manufacturer warranty valid, catches small faults while they are still small, and means the boiler goes into winter in the condition it was commissioned in.
Why it is worth doing
Three reasons, in descending order of how often they actually matter.
- Warranty. Almost every manufacturer warranty requires an annual service by an appropriately qualified engineer, recorded properly. Miss one and cover can lapse — which people typically discover at the moment they need it.
- Catching faults early. A component that is drifting out of tolerance is a cheap fix in September and an emergency callout in January. Servicing is where that difference gets made.
- Safety. Combustion appliances are checked for safe operation, sound flue arrangements and the absence of anything that could produce carbon monoxide.
What a service covers
A proper service is more than a visual inspection and a sticker. Broadly, it involves:
- a check of the appliance's operation, and of any fault history stored in it;
- checking the gas rate and operating pressures against the manufacturer's figures;
- an analysis of the flue gases to confirm combustion is correct;
- inspecting and, where needed, cleaning the burner, heat exchanger and condensate trap;
- checking seals, the flue route and its terminal, and ventilation to the appliance;
- checking system pressure, the expansion vessel and the pressure relief arrangement;
- a look at controls and safety devices, and a record of what was found.
You should be left with a written record. If the engineer finds something outside the scope of a service, it should be reported to you rather than quietly fixed and added to the bill.
What it will not fix
A service is a check on the appliance, not on the heating system around it. Cold spots, slow warm-up and noisy pipework are usually system issues — sludge, air, balancing or a tired pump — and putting them right is separate work.
A good engineer will tell you which of the two you are dealing with. If your radiators have never heated evenly, that is worth raising at the visit rather than assuming a service will resolve it. Our boiler repair page covers what those symptoms usually indicate.
Landlords
Rented property carries separate legal duties. Gas appliances and flues in rented accommodation must have an annual safety check carried out by an appropriately registered engineer, and a record of that check must be provided to the tenant within the required period and kept.
A safety check and a service are not the same thing. The check confirms safety; the service is what keeps the appliance working and the warranty intact. Many landlords have both done in the same visit, which is usually the sensible arrangement.
Gas work and the law
Work on gas appliances must be carried out by an appropriately registered professional. Ask to see registration, and check that it covers the type of appliance and work involved. This applies to a routine service exactly as it applies to a repair.
When to book
Late summer or early autumn is the ideal window. The system has been idle, engineers are less stretched than they are in a cold snap, and anything found can be dealt with in a normal timescale rather than an urgent one.
If you have just had a new boiler fitted, the first service is due a year from commissioning — and it is the one most often forgotten, because the appliance is new and obviously working.
Servicing a heat pump
Heat pumps need an annual check too, but it is a different exercise: clearance and airflow around the outdoor unit, system pressure, the refrigerant circuit, the cylinder and the control settings — particularly the weather compensation curve, which is what determines how efficiently the system runs.
There is no combustion and no flue, so there is no gas safety element at all. More on how these systems work is on our heat pumps page.
Related services
Boiler repair
What common faults mean, and the checks worth making before calling anyone.
Boiler replacement
When a service keeps finding the same problems, what replacement involves.
Boilers
Boiler types, warning signs and how the pieces fit together.
Boiler installation
Fitting a boiler in a new position, or where there was not one before.
Heat pumps
How heat pump systems work, and what their annual check involves.
Heating services
Everything we cover across boilers, heat pumps and heating systems.
Frequently asked questions
- How often should a boiler be serviced?
- Once a year is the standard interval, and it is what almost every manufacturer warranty requires. Skipping a year rarely causes an immediate problem, but it is usually the point at which warranty cover quietly lapses.
- Is an annual service a legal requirement?
- Not for an owner-occupier. Landlords have separate legal duties in respect of gas safety in rented property, including an annual safety check on gas appliances by a registered engineer and a record provided to the tenant.
- What is the difference between a service and a gas safety check?
- A gas safety check confirms an appliance is safe. A service goes further: it also cleans components, checks operating pressures and performance, and is aimed at keeping the appliance working well rather than only confirming it is not dangerous.
- When is the best time of year to book one?
- Late summer or early autumn. The heating has not been under load for months, engineers are less stretched than in midwinter, and anything found can be dealt with before you need the system.
- How long does a service take?
- Typically under an hour for a straightforward appliance in good order. It takes longer if components need cleaning, if access is awkward, or if the engineer finds something that needs investigating.
- Does servicing apply to heat pumps too?
- Yes, though it is a different check — airflow around the outdoor unit, system pressure, the refrigerant circuit, the cylinder and the control settings. There is no combustion and no flue, so there is no gas safety element.