How often should you service a boiler?

Once a year. Nearly every manufacturer warranty requires an annual service carried out by a Gas Safe registered engineer, and it has to be recorded, so missing one can void cover you are still paying for. If you rent the property out, an annual gas safety check on every gas appliance is a separate legal duty on top.

Do boilers need servicing every year even if nothing is wrong?

Yes, and that is rather the point. A service is a safety check and a condition check, not a repair. Most of what it catches, a slowly failing seal, combustion drifting out of range, corrosion starting on a heat exchanger, produces no symptom you would notice until it becomes a breakdown or a safety problem.

Can I service my own boiler?

No. Working on a gas appliance in the UK requires Gas Safe registration by law, and that applies to your own home as much as anyone else's. You can and should do the things around it: check the pressure, bleed radiators, keep the flue terminal clear outside, test the carbon monoxide alarm. Everything behind the boiler casing is a Gas Safe job.

Do radiators get checked during a boiler service?

Not as standard. A service covers the boiler and its flue, not the whole heating system, which is why people are surprised when cold radiators are still cold afterwards. A good engineer will mention anything obvious they notice, but if you want the system balanced or radiators investigated, ask when you book so the time is allowed for.

How long can a boiler go without a service?

Physically it will often run for years without one. The risks are that the warranty lapses, a developing fault turns into a breakdown at the worst time of year, and any combustion problem goes unnoticed. The gap that matters most is the one over a winter, because that is when the appliance works hardest and when a failure is most expensive to fix.

Is it worth having a boiler service?

For a boiler under warranty, yes, without argument, because skipping it can cost you the warranty. For an older boiler out of warranty it is a judgement, but the honest case is that a service is the only routine opportunity anyone has to check combustion and safety. Carbon monoxide is not something you detect by noticing the heating is a bit worse than last year.

What is the difference between a service and a gas safety check?

A gas safety check is a landlord's legal duty: every gas appliance and flue you provide checked at intervals of no more than 12 months, with the record given to the tenant within 28 days. It confirms the appliance is safe. A service goes further and includes cleaning and condition work intended to keep the appliance running well. They overlap but they are not the same thing, and a cheap quote is sometimes one when you assumed the other.

How much does a boiler service cost?

It varies by engineer and by area, and anyone quoting a national figure is guessing at yours. The questions worth asking are what is included, whether a flue gas analysis is part of it, and whether you get a written record afterwards. A price that undercuts everyone locally is usually buying you less time on site, and time on site is the entire product.

Boiler Service: What It Covers and What It Does Not

What a Gas Safe engineer checks during an annual boiler service, why radiators are not included, and whether you can legally do it yourself.

1 September 20266 min readTeesside Premium

The two-minute version

An annual boiler service is a safety and condition check on the boiler and its flue, carried out by a Gas Safe registered engineer. It is not a check of your whole heating system, which is why cold radiators are often still cold afterwards. You cannot legally do it yourself, because any work on a gas appliance requires Gas Safe registration. Most manufacturer warranties are void without a recorded annual service, so for a boiler still under warranty the service usually costs less than skipping it.

September is the sensible month for it on Teesside. Every engineer in the region is busiest the week the first real cold snap arrives, and that is the worst possible time to discover a fault.

What an engineer actually checks

A proper service is more than a visual glance and a sticker. The core of it:

Check	What it means	Why it matters
Flue gas analysis	Measuring what is coming out of the flue with an analyser	The single best evidence that combustion is correct and safe
Flue integrity	Inspecting the flue run and its terminal	A damaged or blocked flue is how combustion gases get back inside
Seals and casing	Checking the case seal and any gaskets	A poor seal can let products of combustion into the room
Burner and heat exchanger	Inspection and cleaning as needed	Where soot, corrosion and early failure show up first
Gas pressure and rate	Confirming the appliance runs to its specification	An appliance running outside spec is inefficient and, eventually, unsafe
Controls and safety devices	Testing that the safety cut-outs actually operate	These are the devices that protect you when something else fails
Pressure and condensate	System pressure, expansion vessel, condensate run	The commonest causes of a boiler locking out in cold weather

At the end you should get a written record of what was checked and found. If you do not get one, you have no evidence for a warranty claim.

What a service does not include

This is where most of the disappointment happens, so it is worth being blunt about it.

Radiators are not part of a standard service. The service covers the boiler and flue. If half your radiators are cold at the bottom, that is sludge in the system and it is a separate job. A good engineer will tell you they noticed. They will not silently fix it inside the service time, because the time was not priced for it.

Balancing is not included. The classic "upstairs boiling, downstairs freezing" complaint is a system balancing issue rather than a boiler fault.

A service is not a repair. If the engineer finds a failed part, that is a repair with its own price. A service tells you the condition; it does not commit anyone to fixing whatever is found for free.

It is not a substitute for a landlord gas safety check, and vice versa — the check is a duty under the Gas Safety (Installation and Use) Regulations 1998, set out by the HSE, while a service is condition work. See the FAQ below, because the two get confused constantly and the difference is legal rather than technical.

If you want any of the above included, say so when booking. Most of them are perfectly reasonable to add. They just need the time allowing for.

Whoever attends should be Gas Safe registered — it is the statutory register, and the HSE's page on gas in the home covers what to do if you smell gas, which is a 0800 111 999 call before it is anyone else's.

Doing it yourself: where the line is

You cannot service your own boiler. Gas work in the UK requires Gas Safe registration, and the law does not carve out an exception for your own home. That is not installer protectionism; it is the same rule that stops anyone else working on your gas without being registered.

What you can usefully do yourself, and what genuinely reduces the odds of a winter breakdown:

Check the system pressure and top up if the manual says to. Low pressure is one of the commonest lockout causes.
Bleed radiators that are cold at the top. Cold at the top is air and you can fix it. Cold at the bottom is sludge and you cannot.
Keep the flue terminal clear outside. Plant growth, a new fence panel or a shed built too close are all real causes of real problems.
Test the carbon monoxide alarm, and fit one if there is not one. This is the cheapest safety item in the house by a distance.
Run the heating briefly in late summer. Finding a fault in September is a booking. Finding it in December is an emergency.

When to book it

The honest answer is now rather than later. Demand for gas engineers across Teesside climbs sharply from the first cold week and stays high until spring, and the same fault costs more to live with in December than in September because the wait is longer.

If your boiler is under warranty, check the service anniversary rather than guessing at it. Manufacturers generally want the service recorded within a window around the installation date, and missing that window is how people discover their cover lapsed only when they need it.

Where a service turns into a replacement conversation, the efficiency measure a new boiler has to carry comes from Approved Document L, and off the gas main a heat pump has its own grant terms worth pricing against oil or LPG.

When we would tell you not to bother

A service is not always the right thing to book, and there are three situations where we would tell you to keep the money. None of them means the boiler can be ignored, only that a service is the wrong spend this month.

If your boiler is under a service plan or manufacturer cover, use it. Booking us instead may invalidate a policy you are already paying for.
If the appliance is genuinely at the end of its life and you have already decided to replace it this year, a service on the way out is money that would be better held back for the replacement. We will say so.
If the actual complaint is cold radiators or poor pressure upstairs, book the system work rather than a service, because a service will not fix it and you will feel short-changed.

Getting it booked

We are Gas Safe registered and cover Middlesbrough, Stockton, Thornaby and the wider Teesside area. Servicing, breakdowns, replacements and landlord gas safety records all go through the same team, and the record lands in your inbox rather than needing chasing.

See what our gas and heating team covers, or the local pages for Middlesbrough and Stockton. If you are a landlord juggling several properties, our between-tenancy checklist covers how the gas check fits around everything else that has to happen in a turnaround.