What Does Boiler Service Include: A Complete Guide

A proper boiler service is a legal requirement for landlords and the single best way to keep your heating system safe, efficient and long-lasting.

In this guide,  I’ll explain every step of a professional boiler service, what the engineer is looking for, and how it protects you from expensive breakdowns and dangerous gas leaks.

What Actually Happens During a Boiler Service?

A boiler service is a thorough 60–90 minute health check and clean carried out by a Gas Safe registered engineer. The goal is to make sure your gas or oil boiler (combi, system or regular) is operating safely and at peak efficiency.

The engineer will typically follow this checklist:

• Visual inspection of the boiler and flue for damage, corrosion or leaks
• Check the gas pressure and gas flow rate
• Test the burner pressure and clean the burner if required
• Remove and clean the heat exchanger (the most important part)
• Clean or replace the main burner, pilot light (if present) and ignition components
• Inspect and clean the condensate trap and pipe (combi & system boilers)
• Check all seals and gaskets for wear
• Test all safety devices (pressure relief valve, thermostat, overheat stat etc.)
• Measure flue gases with a flue gas analyser to check for carbon monoxide
• Check ventilation meets current regulations
• Clean inside the boiler casing and remove any debris
• Reassemble, restart and final performance test
• Issue a Gas Safety Record / Boiler Service Report (landlords legally need this)

Why Is an Annual Boiler Service So Important in the UK?

An annual boiler service is not just “nice to have” – it is essential for four big reasons:

1. Safety – It detects dangerous carbon monoxide leaks before they harm your family or tenants
2. Legality – Landlords MUST have a valid Gas Safe service every 12 months (Gas Safety (Installation and Use) Regulations 1998)
3. Warranty – Almost every UK boiler manufacturer (Worcester Bosch, Vaillant, Ideal, Baxi, Viessmann etc.) makes an annual service a condition of the warranty
4. Savings – A serviced boiler can be 10–15% more efficient, saving £100–£200 a year on gas bills. By contrast, a boiler not serviced every year is far more likely to suffer efficiency loss, safety issues, voided warranties, and unexpected breakdown costs.

Understanding how often you should service your boiler helps ensure you stay compliant with UK law, protect your warranty, and avoid preventable breakdowns.

How Long Does a Boiler Service Take?

A full service on a modern combi boiler usually takes 45–90 minutes. Older conventional or system boilers with hot-water cylinders can take up to 2 hours because more components need cleaning.

How Much Does a Boiler Service Cost?

Typical prices (2025):

• Standalone boiler service: £70–£120
• Boiler service included in a cover plan: £8–£25 per month Landlords with multiple properties often get discounts for 3+ boilers.

What’s the Difference Between a Boiler Service and a Gas Safety Check (CP12)?

Many people get confused:

• Boiler Service = full clean + safety check + efficiency optimisation
• Gas Safety Check (Landlord’s CP12) = safety-only inspection (no cleaning) A proper boiler service always includes everything needed for a CP12, so one visit covers both.

How to Prevent Boiler Problems in the Future

Simple habits that dramatically reduce breakdowns:

• Keep the boiler area clean and well ventilated
• Bleed radiators every autumn
• Keep the pressure between 1–1.5 bar when cold
• Set heating to come on for 15–30 minutes daily in summer to keep pumps moving
• Fit a magnetic system filter (catches rust) – highly recommended
• Install carbon monoxide alarms on every level
• Book your service in spring or summer (cheaper and easier to avoid winter rush)

FAQs

Can I service my own boiler to save money?

No. Only a Gas Safe registered engineer is legally allowed to work on gas boilers in the UK. DIY servicing invalidates your warranty and insurance.

Will the engineer need to turn my heating off for long?

Usually only 1–2 hours maximum. Most engineers visit in the morning so you have heat again by lunchtime.

Do oil boilers need servicing too?

Yes – OFTEC-registered engineers service oil boilers annually in exactly the same way. The process is very similar.

My boiler is only 2 years old – does it still need servicing?

Yes. New boilers collect dust and debris surprisingly quickly and manufacturers insist on annual servicing to keep the 10–12 year warranty valid.

Can I get a same-day or emergency boiler service?

Most companies offer next-day slots, but true same-day is rare outside normal servicing (it becomes a breakdown call-out, £150–£300).

Stay warm, The Boilers2Go Team