Does your boiler warranty need an annual service?

A boiler warranty is the manufacturer’s promise to repair faults for a set time after it is fitted. In return, most makers ask you to do a few things. The most common is an annual service. If you skip it, the warranty can be refused when you need it.

This guide covers what to check, what records to keep, and why warranties are often lost in London’s rented flats.

What most boiler warranties ask for

Every manufacturer writes its own terms, and they can differ by model and by who installed it. So treat this as a checklist, not a promise of what your document says.

Common condition	What it means for you
Registration after installation	The boiler is registered with the maker, often by the installer, within a set time
Annual service	A service every year, usually within 12 months of installation and then of each service
Gas Safe registered engineer	The service is done and recorded by someone on the Gas Safe Register
Service record kept	You can show a dated record for each year
Water treatment	Some terms mention a system clean, inhibitor or filter at installation
Genuine parts	Repairs use the maker’s approved parts

If you do not have the paperwork, look for the boiler’s serial number on its label and contact the manufacturer. They can usually confirm whether it was registered and what terms apply.

Why the service matters to the maker

A manufacturer is agreeing to pay for repairs. It wants to know the boiler has been looked after. An annual service checks that gas burns properly, that the flue is safe, and that parts are not wearing out early. It also picks up problems that the warranty may not cover at all, such as damage from sludge or scale.

HSE gives the same general advice for any gas appliance. It recommends servicing in line with the manufacturer’s instructions, or every year if there are no instructions, unless a Gas Safe registered engineer advises otherwise.

Hard water and warranty claims

North and east London water is hard. Thames Water’s 2025 reports put average hardness at 268 mg/l in Hackney West, 276 mg/l in Kentish Town and 273 mg/l in Tottenham South. You can see the zone figures in our guide to hard water and your boiler.

Some warranty terms exclude damage caused by scale or by dirty system water. Guidance says scale protection should be fitted where hardness is over 200 ppm, and every Thames zone in the area is above that. If a combi fails early because its plate heat exchanger is full of limescale, the maker may ask whether scale protection and water treatment were in place. A service record that shows inhibitor checks and filter cleans helps here.

How warranties get lost in London lets

Camden has 35.6% of households renting privately and Tower Hamlets 38.2%, according to the Census 2021 area pages from ONS. With that much renting, boilers often change hands without the paperwork:

• A flat is sold and the warranty card stays in a drawer in the old owner’s new home.
• A landlord books the annual gas safety check but not a service, thinking they are the same.
• A tenant cannot be reached and the service slips past the 12 month mark.
• An agent changes and the service history is not passed on.

The second point catches a lot of people. A landlord gas safety record proves the appliances were safe on the day. A service is maintenance. They are separate, and many landlords book them together on one visit. Our guide on the difference between a gas safety check and a boiler service explains this in full.

Keeping your service record

Keep the record from every service. A good record shows the date, the engineer’s name and Gas Safe number, the boiler make and model, what was checked, readings taken and any parts replaced. Many manufacturers’ manuals include a service log page at the back. Ask the engineer to fill it in as well as giving you their own sheet.

Store a photo of each record on your phone. If you sell or let the property, pass copies on. A buyer or tenant can then see the boiler’s history.

What a warranty does not usually cover

Warranties normally cover faults in the boiler itself. They often do not cover:

• problems with the wider heating system, such as leaking radiators or a faulty pump outside the boiler
• damage from frozen condensate pipes, sludge or scale
• faults caused by work done by someone who was not qualified
• the cost of access if the boiler is boxed in

These depend on your terms. If you are not sure, ask the manufacturer before you book a repair.

Booking the service

A boiler service is best booked a little before the 12 month date so it does not slip. In north London, plan for access. Boilers in flats in Kentish Town or Gospel Oak are often in a kitchen cupboard or airing cupboard, and engineers need to reach the flue too. Our Camden area page covers the homes most common there.

Gas work in the UK must be done by a Gas Safe registered engineer. Ask to see their Gas Safe ID card and check that it lists the right work category for a domestic boiler. The price is confirmed when you book, based on the boiler and its access.