What is actually checked in a boiler service?

Not every service is the same, and because most people are not stood watching, it is worth knowing what should happen. A service that takes ten minutes and ends with a sticker is not a service.

The checks

1. 1

   Gas pressure and gas rate

   Confirms the boiler is being fed correctly and burning the right amount of gas. Under or over gassing wastes money at best and is unsafe at worst.

2. 2

   Flue gas analysis

   An analyser probe in the flue reads the combustion. Those numbers are the single best indication that the boiler is burning cleanly and safely, and they get recorded.

3. 3

   The flue and its seals

   Inspected along its length where it can be seen, inside and out, checking it is sealed and clear. This is the check that matters most for carbon monoxide.

4. 4

   Case seals and combustion chamber

   Opened up, checked, cleaned where needed, then sealed properly on the way back. A case that is not resealed correctly is a genuine hazard.

5. 5

   Condensate trap

   Cleared. A silted trap is a very common cause of a boiler locking out in the middle of winter.

6. 6

   System pressure and expansion vessel

   The vessel loses its charge over time, which then shows up as pressure that keeps climbing and dropping. Recharging it is quick, and finding it early avoids a discharge outside.

7. 7

   Safety devices and controls

   Tested rather than assumed, along with the thermostat and timer working as they should.

How to tell you got a real one

• The engineer had the case off the boiler
• They used a flue gas analyser
• You got a written record with readings on it, not just a date
• They told you what they found, including anything borderline
• It took the best part of an hour

When to book it

Late summer or early autumn. Everyone rings in the first cold week, which is when every heating engineer is already out on breakdowns. Book it while nothing is wrong and it is an hour of your time.