A boiler service is planned maintenance. An engineer checks that your boiler is safe and working well, even when nothing is wrong. A boiler repair is corrective work. An engineer finds out why your boiler has stopped working properly and fixes it.
A service can reveal a fault, but it does not automatically fix it. Repairs and parts are usually quoted separately.
If your boiler works normally and it has been about 12 months since its last check, book a service. If it has stopped working, keeps losing pressure, shows an error code or is leaking, book a repair. If you smell gas or a carbon monoxide alarm sounds, don’t book anything. Act on the emergency steps in the safety section below.
Quick Comparison: Boiler Servicing vs Boiler Repair
| Boiler service | Boiler repair | |
|---|---|---|
| Main purpose | Prevent problems and check safety | Find and fix a fault |
| When you need it | Once a year, or as the manufacturer advises | When the boiler breaks down or behaves oddly |
| Planned or urgent? | Planned, booked ahead | Often urgent, especially in winter |
| What the engineer does | Inspects, tests, cleans and records results | Diagnoses the cause, then repairs or replaces parts |
| Parts included? | Usually not, unless the quote says so | Quoted separately for each job |
| Typical London cost | Fixed price, often around £110–£180 | Varies by fault, often £200–£500 |
| Result | A record of your boiler’s condition | A boiler that works again |
Prices are indicative. See the cost section below for how to read them.
What Is a Boiler Service?
A boiler service is a scheduled check-up carried out by a Gas Safe registered engineer. It confirms that your boiler is burning gas safely, running efficiently and showing no early signs of failure.
Think of it like a dentist check-up. Nothing hurts yet, but the dentist spots small problems before they become painful ones.
What happens during a boiler service?
Every boiler is different, so the engineer follows the steps in your manufacturer’s instructions. In general, a good service includes:
- A visual inspection. The engineer checks the boiler casing, the flue (the pipe that carries fumes outside), the condensate pipe and any visible pipework. They look for leaks, rust, soot marks and damage.
- Safety checks. The engineer checks that the boiler’s safety devices work. They also check for gas leaks around connections.
- Combustion analysis. Using a flue gas analyser, the engineer measures what comes out of the flue. This shows whether the gas is burning cleanly and safely. It is one of the most important parts of the visit.
- Gas pressure checks. The engineer confirms the boiler is getting the right amount of gas.
- Internal inspection and cleaning. With the casing off, the engineer examines parts such as the burner, heat exchanger, ignition electrodes, fan, seals and pump. They clean what needs cleaning and check for wear.
- System checks. The engineer checks water pressure, the expansion vessel, the condensate trap and the controls.
- A written record. You should receive a service record that lists what was checked, what was found and anything that needs attention.
What a boiler service does not usually include
- Replacement parts
- Repairs to faults found during the visit
- A powerflush or full system cleanse
- Work on radiators, taps or other plumbing
If your engineer finds a problem, they should explain it clearly, give you a written quote and let you decide what to do. The only exception is a serious safety risk, where they may need to switch the boiler off to protect you.
How long does a boiler service take?
Most services take about 45 to 60 minutes for a standard gas boiler. Which? advises that a decent service should last at least 30 minutes, so a visit that takes 10 minutes is a warning sign. Older boilers, poorly maintained boilers or boilers that haven’t been serviced for years can take longer.
Why does the service matter if the boiler works fine?
Many faults begin quietly. A worn seal, a dirty burner or a slowly dropping pressure reading can all go unnoticed for months. A service picks these up before they turn into a no-heating emergency on the coldest night of the year.
A service also checks things you can’t see or smell. Carbon monoxide has no colour, taste or smell, so a boiler that looks fine can still burn poorly.
What Is a Boiler Repair?
A boiler repair is work to diagnose and fix a specific fault. It starts with a problem: no heating, no hot water, a leak, an error code or a boiler that keeps switching off.
Unlike a service, a repair has no fixed checklist. The work depends on what the engineer finds.
What happens during a boiler repair?
- You describe the symptoms. Tell the engineer what you’ve noticed, when it started and any error codes on the display. Details like “it only fails when the hot tap is on” can save time.
- The engineer diagnoses the fault. Symptoms point to a cause but don’t prove it. For example, a boiler that keeps losing pressure might have a leaking radiator valve, a faulty pressure relief valve or a failed expansion vessel. The engineer tests to find which one it is.
- You get a quote. A fair quote lists the fault, the part, the labour and any extra visit. Ask for it in writing before you agree.
- The repair is carried out. The engineer fits or fixes the part. If the part isn’t on the van, they may need to order it and return.
- The engineer tests and hands over. They check that the boiler runs through a full cycle, that safety devices work and that heating and hot water are back. They should also tell you what they did and whether anything else needs attention.
Which faults need a repair, not a service?
This table shows how common symptoms usually point to one or the other. It is a guide only. Only an engineer can confirm the cause.
| What you notice | Usually needs | Possible causes |
|---|---|---|
| No heating or hot water | Repair | Failed pump, diverter valve, PCB, thermostat or ignition fault |
| Heating works but not hot water (or the other way round) | Repair | Diverter valve, motorised valve or thermostat |
| Pressure keeps dropping | Repair | Leak, faulty pressure relief valve or failed expansion vessel |
| Error code or lockout | Repair (check manual first) | Depends on the code; some are simple resets |
| Water leaking from the boiler | Repair, and soon | Failed seal, corroded part or loose joint |
| Banging, gurgling or whistling | Repair or service | Scale, trapped air, sludge or a failing pump |
| Radiators cold at the bottom | Repair or system clean | Sludge in the system |
| Boiler works fine, due its yearly check | Service | Routine maintenance |
| Boiler hasn’t been checked for years | Service first | Hidden wear or poor combustion |
How long does a boiler repair take?
Simple fixes, such as resetting a lockout or topping up pressure, can take under an hour. Replacing a pump or circuit board often takes one to two hours. Bigger jobs, such as a heat exchanger, can take longer or need a second visit for parts.
Does a Boiler Service Include Repairs?
No, a boiler service doesn’t automatically include repairs. A service finds and records problems. Fixing them is usually a separate job with its own cost.
This surprises many people. They book a service, the engineer finds a worn part, and a repair quote follows. That isn’t a trick. It’s how the two jobs are priced. The service fee covers the engineer’s time and checks. The repair covers the part and the extra labour.
What happens if the engineer finds a fault?
Here is a typical example. A homeowner in a London terraced house books a yearly service. During the combustion test, the engineer sees that the flame isn’t burning evenly. After removing the burner, they find it is partly blocked and a seal is worn. They explain this, quote for a new seal and a clean, and the homeowner agrees. The boiler gets the repair on the same visit.
Without the service, the blockage could have grown until the boiler locked out in January.
When a fault comes up, the engineer’s findings usually fall into one of three groups:
- Safe to continue. An advisory note. The boiler can keep running, but the part should be watched or replaced soon.
- Repair recommended. A fault that will probably cause a breakdown or waste energy.
- Unsafe. The engineer must switch the boiler off and may issue a warning notice. You shouldn’t use the boiler until it’s fixed.
You are free to get a second quote for non-urgent repairs. You can’t ignore an unsafe boiler.
Can a boiler be serviced if it isn’t working?
Usually yes, but the engineer will need to fix the fault first. A broken boiler can’t complete the tests a service needs. In that case, book a repair visit. Once it’s working again, you can book the service, or the engineer may offer to combine them. Ask when you book.
Do You Need a Boiler Service or a Boiler Repair?
If your boiler is working normally, book a service. If it isn’t working properly, book a repair. The decision is simple once you work through a few questions.
Step-by-step: how to decide
- Do you smell gas, or is a carbon monoxide alarm sounding? If yes, stop here and follow the emergency steps in the next section.
- Is the boiler producing heating and hot water as normal? If yes, go to step 3. If no, book a repair.
- Is it showing an error code, leaking, losing pressure or making new noises? If yes, book a repair. If no, go to step 4.
- Has it been more than 12 months since the last service? If yes, book a service. If no, you probably don’t need anything yet.
- Does it work, but something feels “off”? Examples are radiators taking longer to warm up or slightly higher bills. Book a service and tell the engineer what you’ve noticed. They can often find the cause during the visit.
When to book a routine service
- It’s been about a year since the last one.
- You’ve just moved into a home and don’t know the boiler’s history.
- The boiler works but is noticeably slower or noisier than before.
- Your warranty or boiler cover requires an annual check.
- Winter is coming and you want to reduce the risk of a breakdown.
When to book a repair
- No heating or no hot water
- Pressure keeps falling and needs topping up often
- Error codes that return after you reset the boiler
- The boiler switches itself off repeatedly
- Water is leaking from or around the boiler
- Loud banging, grinding or other unusual noises
What about a noisy boiler that still works?
Book a visit soon, but you can usually treat it as a service-plus-diagnosis, not an emergency. Tell the engineer about the noise when booking so they can allow time to investigate. If the noise is loud banging or grinding, or comes with a leak, treat it as a repair.
When Should You Stop Using Your Boiler?
Stop using your boiler straight away if you smell gas, if a carbon monoxide alarm sounds, or if you see soot, scorch marks or a yellow or orange flame on a boiler that should burn blue. These are safety emergencies, not service or repair questions.
If you smell gas or suspect a leak
- Open doors and windows.
- Turn off the gas at the meter if it is safe to do so.
- Don’t use light switches, naked flames, phones or electrical equipment near the smell.
- Leave the property.
- Call the National Gas Emergency Service on 0800 111 999 (free, 24 hours).
If a carbon monoxide alarm sounds
- Move everyone outside into fresh air.
- Call 999 if anyone feels unwell.
- Don’t go back in until the alarm has been investigated.
- Have a Gas Safe registered engineer inspect the boiler before you use it again.
Symptoms of carbon monoxide poisoning include headaches, dizziness, nausea, breathlessness and tiredness. They can feel like the flu, which is why a working carbon monoxide alarm matters. Fit one in any room with a gas appliance and test it regularly.
How Much Do Boiler Servicing and Boiler Repair Cost in London?
In London, a boiler service often costs around £110 to £180, while a boiler repair often costs £200 to £500, depending on the fault. Prices vary by company, boiler type and how urgent the job is.
Boiler service cost in London
Nationally, Which? reports that a one-off gas boiler service typically costs £70 to £110. Prices in the capital tend to be higher because of labour, parking and travel costs. One recent price guide puts a London or high-cost-area service at £110 to £180.
What affects the price:
- Boiler type. Combi, system and conventional boilers take different amounts of time.
- Boiler age and access. An old boiler in a cramped cupboard takes longer than a new one on an open wall.
- Booking time. Evening, weekend and urgent slots may cost more.
- What’s included. Some companies include a written report or minor adjustments. Others charge extra.
Boiler repair cost in London
Repair costs depend on the fault. One 2026 cost guide gives an average repair, such as a fan, pump, circuit board or diverter valve, at £200 to £500 in London and the South East, with major jobs like a heat exchanger replacement rising higher. A simple fix such as re-pressurising the system can cost far less.
What affects the price:
- The part that has failed, and whether it’s in stock
- How long the diagnosis takes
- Labour rates and call-out fees
- Whether it’s an emergency or out-of-hours visit
- Your boiler’s age, since older models can have harder-to-find parts
What does a repair usually cost after a service?
In a June 2025 survey, Which? found that the average one-off repair following a boiler service cost £156. That’s a useful figure for budgeting. Many repairs after a service are smaller jobs, not major breakdowns.
How to read a repair quote
A good quote should show:
- The fault in plain English
- The part and its cost
- Labour charges
- Any call-out or diagnostic fee
- Whether a return visit is needed
- Any guarantee on the work
If a quote is vague, ask for more detail. If it’s for a large amount, a second opinion is reasonable.
Is it cheaper to service or to wait for a breakdown?
A service costs less than most repairs, and it removes the cost of being without heating in winter. But a service can’t promise your boiler won’t fail. What it does is reduce the odds and catch problems early, when they’re often cheaper to fix.
How Often Should a Boiler Be Serviced?
A gas boiler should be serviced once a year by a Gas Safe registered engineer. This is the standard advice from manufacturers and bodies such as the Energy Saving Trust.
Some manufacturers set different rules, so check your boiler’s manual or warranty documents. Newer boilers sometimes come with long guarantees, but those often depend on a yearly service by a registered engineer. If you miss one, the warranty may be affected. Always read the terms to see exactly what applies to you.
When is the best time to book?
Late summer or early autumn is ideal. Engineers are less busy than they are in the first cold snap, so you get more choice of appointment times. If the engineer finds something that needs fixing, you have time to sort it before you rely on the heating.
Is the boiler service the same every year?
The checks are similar, but the engineer compares each year’s results with the last. Small changes, such as slowly falling efficiency or a part that is wearing, are easier to catch when there is a record to compare against. Keep your service records in one place. They also help if you sell the property or make a warranty claim.
What if I’ve missed a service or two?
Book one as soon as you can. Tell the engineer how long it’s been, because they may need extra time to inspect and clean the boiler. Don’t wait until winter.
Is a Boiler Service the Same as a Gas Safety Check?
No. A boiler service and a gas safety check are two different jobs. A service is maintenance. A gas safety check is a safety inspection of gas appliances and flues, and it’s a legal requirement for landlords.
| Boiler service | Landlord gas safety check | |
|---|---|---|
| Purpose | Maintain the boiler and keep it efficient | Confirm gas appliances and flues are safe |
| Who needs it | All boiler owners (recommended) | Landlords of rented homes (legal duty) |
| Scope | The boiler, in detail | All gas appliances, pipework and flues provided by the landlord |
| Result | Service record | Gas Safety Record |
| How often | Yearly (or per manufacturer) | At least every 12 months |
What London landlords need to know
If you rent out a property in London, the Gas Safety (Installation and Use) Regulations require a yearly gas safety check by a Gas Safe registered engineer. You must keep the Gas Safety Record for at least two years. You must give a copy to existing tenants within 28 days of the check, and to new tenants before they move in.
A service doesn’t replace this check. Some engineers offer both in one visit, which can save time and money. Ask for both to be recorded separately, so your paperwork is clear.
If you’re a tenant, your landlord is responsible for the safety and repair of the boiler. Tell them quickly if you spot a fault or smell anything unusual.
Can a Boiler Service Prevent Expensive Repairs?
A boiler service can reduce the risk of breakdowns, but it can’t guarantee your boiler will never fail. That’s the honest answer, and it’s why you should be wary of anyone who promises otherwise.
Here is what a service can realistically do:
- Spot early wear. A tired seal, a dirty burner or a weak ignition lead can be replaced before it causes a lockout.
- Catch unsafe combustion. Poor burning can be fixed before it becomes a danger.
- Improve efficiency. A clean, well-set boiler wastes less fuel.
- Keep a record. Patterns over several years help you decide when a boiler is nearing the end of its life.
Here is what it can’t do:
- Predict every failure. Electronic parts such as circuit boards can fail without warning.
- Fix faults on its own. Repairs are separate.
- Make an old boiler new.
So the best approach is to treat servicing and repair as partners. Servicing lowers the odds of a breakdown. Repair is there when something goes wrong anyway.
Should You Repair or Replace Your Boiler?
Repair is usually sensible for a newer boiler with a single faulty part. Replacement is worth considering when the boiler is old, breaks down often or needs an expensive part. There’s no single rule, but these points help.
| Factor | Points to repair | Points to replace |
|---|---|---|
| Age | Under about 8–10 years | Over about 12–15 years |
| Repair cost | Small compared with a new boiler | A large share of a new boiler’s price |
| Breakdown history | Rare faults | Repeated faults |
| Parts | Easy to find | Discontinued or hard to source |
| Efficiency | Still running well | Bills are rising and heat is patchy |
| Warranty | Still covered | Expired |
Ask your engineer for an honest view. A trustworthy one will tell you when a repair is good value and when it’s money you’ll lose. If you’re weighing up a new boiler, read our guide to boiler replacement in London for costs and options.
Servicing and Repair in London Homes: What’s Different?
London homes bring a few local challenges that affect both servicing and repairs. Knowing them helps you ask the right questions.
- Hard water. Much of London has hard water, which can cause limescale. Scale can build up in the heat exchanger and cause “kettling” noises, reduced efficiency and, over time, failures. An engineer can check for signs of this during a service.
- Flats and conversions. Many London boilers sit in cupboards, kitchens or loft spaces with limited access. This can make the service longer. Flue routes in converted buildings can also be awkward, so ask the engineer to check them carefully.
- Older properties. Victorian and Edwardian homes often have older pipework and radiators. Sludge can build up in older systems and cause cold spots and pump strain.
- Frozen condensate pipes. In a cold snap, the external condensate pipe on a condensing boiler can freeze and shut the boiler down. It’s a common winter call-out, and it’s often a quick fix. A service can check that the pipe is correctly installed and insulated.
- Parking and access. In busy areas, engineers may need parking permits or longer travel time. Good companies explain any extra charge upfront.
- Rented homes. London has a large rental market, so landlords and tenants should know who is responsible for what. See the gas safety section above.
How to Choose a Boiler Engineer in London
Choose an engineer who is on the Gas Safe Register, gives written quotes and explains problems in plain English. The law says anyone working on gas appliances must be registered.
Checklist before you book
- Check Gas Safe registration. Ask for the engineer’s Gas Safe ID card, or look them up on the Gas Safe Register website or by phone. Make sure the card shows they’re qualified for the type of work, such as boilers.
- Ask what’s included in the service price. Check whether it covers a written report, minor adjustments and combustion analysis.
- Ask how repairs are priced. Find out if there is a call-out fee, a diagnostic fee or a labour rate per hour.
- Ask for written quotes. Don’t agree to major work without one.
- Check reviews and history. Look for recent reviews that mention clear communication and fair pricing.
- Ask about guarantees. Find out how long the repair or part is covered.
- Check insurance. A reputable company will have public liability cover.
Red flags
- Pressure to decide on the spot
- A very low price that doesn’t match the market
- Refusal to show Gas Safe ID
- Vague explanations of what’s wrong
- Demands for full payment upfront
- A “service” that takes only a few minutes
How to Book the Right Appointment (Step by Step)
- Note your boiler’s make, model and age. You’ll usually find these on the front or in the manual.
- Write down the symptoms. Include error codes, noises, leaks and when they happen.
- Say whether it’s a service, a repair or both. If you’re not sure, describe what you’ve noticed. A good company will help you choose.
- Ask for the price and what it covers. Confirm the service fee, any call-out fee and how repairs are quoted.
- Choose your slot. If the boiler is working, pick a time that suits you. If it’s not, ask about the earliest available visit.
- Clear access. Make sure the engineer can reach the boiler, and have your last service record ready.
- Ask for your paperwork afterwards. Keep the service record or repair invoice in a safe place.
Frequently Asked Questions
What is the difference between boiler servicing and boiler repair?
A boiler service is planned maintenance that checks safety and performance, even when nothing is wrong. A boiler repair fixes a specific fault, such as no hot water or a leak. A service helps prevent problems. A repair solves one that has already happened.
Does a boiler service include repairs?
No, not automatically. A service finds and records faults, but repairs and parts are normally quoted separately. If the engineer finds a problem, they should explain it and give you a written quote. Some boiler care plans include repairs, so check your terms.
Can a boiler service find a fault?
Yes. Combustion analysis, pressure checks and an internal inspection can reveal developing faults, such as a blocked burner, a worn seal or a poor flue reading. Finding a fault early often makes it cheaper to fix. A service can’t predict every failure, especially sudden electronic faults.
Do I need a boiler service if my boiler works fine?
Yes, it’s still recommended. Many problems, including unsafe combustion, give no obvious sign. A yearly service checks safety and efficiency, and it may be required to keep your warranty valid. It’s also a chance to catch small issues before winter.
How often should a boiler be serviced in London?
Once a year, as with any gas boiler in the UK. Follow your manufacturer’s instructions, because some set specific requirements. Late summer or early autumn is a good time to book, before demand rises.
How much does a boiler service cost in London?
Many London services cost around £110 to £180, though prices vary by company and boiler type. Nationally, Which? reports £70 to £110 for a one-off gas boiler service. Always ask what’s included before you book.
How much does a boiler repair cost in London?
Many common repairs cost around £200 to £500, while major jobs such as a heat exchanger can cost more. Simple fixes can cost less. The final price depends on the fault, the part and the labour, so ask for a written quote.
Should I book a service or a repair if my boiler keeps losing pressure?
Book a repair. Repeated pressure loss usually points to a leak or a faulty part, such as a pressure relief valve or expansion vessel. A routine service isn’t designed to diagnose and fix this. Tell the engineer how often you top up the pressure.
Is a boiler service the same as a gas safety check?
No. A service maintains the boiler. A gas safety check inspects gas appliances and flues for safety, and landlords must have one every 12 months. A service doesn’t replace a landlord’s gas safety check, although some engineers can do both in one visit.
When should I stop using my boiler?
Stop at once if you smell gas, if a carbon monoxide alarm sounds, or if you see soot or scorch marks. Leave the property if you smell gas and call 0800 111 999. For a faulty boiler without these signs, switch it off and book a Gas Safe engineer.
Conclusion: Which Should You Book?
Boiler servicing and boiler repair do different jobs, and most households need both at different times. A service keeps a healthy boiler safe, efficient and well documented. A repair gets a faulty one working again.
Use this rule of thumb:
- Working normally and due a check? Book a service.
- Not working properly? Book a repair.
- Smell gas or hear a carbon monoxide alarm? Leave, then call the emergency number.
Whichever you need, choose a Gas Safe registered engineer, ask what’s included, and get repair quotes in writing. That way you know what you’re paying for and why.
Not sure whether your boiler needs a service or a repair? Boiler Installer London, your local Gas Safe registered team in London, can talk through your boiler’s symptoms and book the right visit. Book a boiler service or request a repair assessment today.