Boiler servicing and repairs

The short answer

A gas boiler should be serviced annually by a Gas Safe registered engineer, who checks combustion, seals, flue and controls. Common faults are pressure loss, failed diverter valves, blocked condensate pipes freezing in winter and faulty thermostats. Once a boiler is beyond around twelve to fifteen years old and parts are becoming scarce, repeated repair usually costs more than replacement over time.

What the work involves

A service includes a flue gas analysis, checking the heat exchanger and seals, testing safety devices and controls, and issuing a service record. Repairs range from a five-minute repressurise to a full component replacement.

Rules and consents in Scotland

All gas work must be carried out by a Gas Safe registered engineer — this is a legal requirement. Landlords must hold a current annual gas safety record for each let property. Boiler replacement requires building standards compliance and notification.

What commonly goes wrong

Skipping annual servicing to save money, which invalidates most manufacturer warranties and misses early signs of a failing heat exchanger.

What it usually costs

Indicative ranges only, to help you judge a quote. They are not an estimate for your property — only the business doing the work can give you that.

• An annual service is a modest fixed cost and is often bundled into a maintenance plan.
• Common component repairs — pumps, valves, PCBs — vary widely; a PCB can be a large share of the value of an old boiler.
• Replacement costs depend on boiler type, whether the system is being converted from a tank system, and flue routing.
• Tenement flats sometimes need a specific flue arrangement, which adds cost.

What to do, in order

1. 1Book a service annually, ideally in late summer before the heating season.
2. 2Check the engineer's Gas Safe registration number before work starts.
3. 3Keep the service record — it matters for warranty and, for landlords, is a legal requirement.
4. 4Insulate the external condensate pipe to prevent winter freezing.
5. 5Ask for the age and expected remaining life when a significant repair is quoted.
6. 6Compare the repair cost against replacement before spending on an old boiler.

Local detail for the Lothians

• Edinburgh's cold snaps regularly freeze external condensate pipes on tenement rear elevations, causing boilers to lock out; insulating the pipe prevents most call-outs.
• Flue positions in tenement flats are constrained by shared elevations and, in listed buildings, by consent requirements.
• Some Lothians rural properties are off the gas grid and run on LPG or oil, which needs a differently qualified engineer.
• Older tank-fed systems remain common in Edinburgh's period flats and conversion to a combi involves more than swapping the boiler.

When you need a professional

A Gas Safe registered heating engineer for anything involving gas; an OFTEC registered engineer for oil.

Common questions

How often should a boiler be serviced?

Once a year. It is also normally a condition of the manufacturer's warranty.

When is it worth replacing rather than repairing?

Generally once the boiler is well past ten years old and a major component such as the heat exchanger or PCB has failed.

Related pages

• Central heating repairs

  Cold radiators, noisy systems, power flushing and control upgrades.

• Plumbing and leaks

  Leaks, burst pipes, overflows and the water damage that follows in flats.

• Electrical safety checks

  EICRs, consumer unit upgrades and the certification landlords must hold.