Moving house? The boiler checks worth making

A boiler can look tidy during a house viewing and still leave the new owner with an expensive surprise. Before exchange, the useful questions are not simply whether it switches on, but what it is, how old it is, whether it has been maintained, how the whole heating system performs and whether the paperwork supports the seller’s answers.

A normal property survey is not a boiler service. Surveyors generally report visible condition and may test basic operation, but they do not dismantle or internally inspect a gas appliance. If heating condition matters to your purchase, arrange the right check while you still have time to understand the result.

Boiler checks before you buy: the short list

• Identify the make, model, boiler type and approximate installation date.
• Ask for service records, repair invoices and the current warranty terms.
• Check for a Building Regulations compliance certificate where one should exist.
• Run the heating and hot water long enough to see whether they perform normally.
• Look for visible leaks, corrosion, staining, repeated fault codes or falling pressure.
• Test the controls and ask the seller to leave their instructions.
• Have concerns assessed by a suitably qualified Gas Safe registered engineer.

1. Identify the boiler and system

Photograph the front of the boiler and its data label only where that label is accessible without removing the case. Record the brand and exact model. Baxi, Worcester Bosch and Ideal model families can contain combi, system and heat-only versions with different controls and parts.

Work out whether the home has a combi boiler, a hot-water cylinder, or a traditional cylinder-and-loft-tank arrangement. That affects available cupboard space, hot-water performance and the cost and disruption of a future replacement. Ask which rooms contain the cylinder, programmer, pumps, zone valves, expansion vessel and stop taps.

If the boiler’s age is unclear, the seller’s installation paperwork, service history and manufacturer may help. A vague claim that it is “fairly new” is not a substitute for a date.

2. Ask for the records

Request the boiler’s installation and commissioning record, service history, repair invoices and user instructions. For a relatively new boiler, ask whether the manufacturer warranty is active, whether it can transfer to a buyer and what continued servicing is required. Citizens Advice notes that if a boiler was installed before you bought the home, you should check the warranty terms rather than assume cover transfers.

A missing service record does not prove a boiler is unsafe, and a stamped book does not guarantee that no fault has developed since the last visit. The records show how the appliance has been treated and give an engineer useful history.

3. Look for the compliance certificate

In England, a new or replacement boiler is controlled building work. When eligible work is completed by a registered competent person, the installer can self-certify it and notify the local authority. GOV.UK says the resulting certificate can be used as evidence of compliance and should also appear in solicitors’ searches.

If the seller cannot produce a certificate, raise it with your conveyancer rather than trying to solve the legal position yourself. Requirements and processes differ across the UK, and the appropriate evidence depends on where and when the work was carried out.

The Building Regulations certificate is not the same as a service record, warranty registration or landlord gas-safety record. Each proves something different.

4. Read the EPC carefully

The seller or agent must make a valid Energy Performance Certificate available for most marketed homes. An EPC rates the property from A to G and contains information about estimated energy use and suggested improvements. You can download certificates for England, Wales and Northern Ireland through the official GOV.UK register; Scotland has a separate service.

Check the heating description, boiler type, controls and recommendations, but remember that an EPC is an energy assessment under standard assumptions. It is not a condition report or gas-safety inspection. An older EPC may also pre-date later heating work, even though EPCs can remain valid for ten years.

5. Test heating and hot water properly

With the seller’s permission, turn up the room thermostat and confirm that the boiler responds. Give radiators enough time to warm. Check whether some remain cold, heat only at the top, make persistent noises or show signs of leakage at valves. One cold radiator may be a local issue; widespread poor circulation can point to controls, balancing, pump or system-water problems that need diagnosis.

Run hot taps and a shower. On a combi, look for stable hot-water temperature and sensible flow, including what happens when another outlet opens. With a cylinder system, ask how long the water takes to heat, how it is scheduled and whether an immersion heater provides backup.

Do not force controls, remove covers, operate unknown isolation valves or attempt to reproduce an intermittent fault. Record what happened and arrange a professional check.

6. Look without dismantling

You can make useful observations without touching the inside of a boiler:

• water marks, drips or corrosion below the appliance and nearby pipework;
• a pressure gauge that is very low, very high or repeatedly changes after topping up;
• damage to the visible flue terminal or staining around it;
• missing controls, loose casing panels or improvised pipework;
• error codes or a history of frequent resets;
• condensate pipework that appears damaged or has caused past leaks;
• unusual banging, grinding or kettling noises.

Never remove the case, inspect combustion parts or climb to examine a flue. Internal gas-boiler checks should only be carried out by a Gas Safe registered engineer with the correct appliance qualification.

7. Test the controls

Confirm that the room thermostat, programmer, cylinder thermostat and any smart control actually communicate with the system. Ask the seller to demonstrate normal heating and hot-water schedules, then obtain the manuals, account-transfer instructions and any hub or receiver details.

A smart thermostat left linked to the seller’s account can become an avoidable moving-day nuisance. Arrange a proper ownership reset rather than asking for someone else’s password. Check that physical override controls still work.

8. Check carbon-monoxide protection

Identify every carbon-monoxide alarm, read its replacement date and use its test button as the manufacturer directs. An alarm is an essential extra layer of protection but does not certify the boiler as safe.

If an alarm sounds or occupants develop possible carbon-monoxide symptoms, get everyone into fresh air, seek medical advice and follow the National Gas Emergency Service guidance. Do not continue a property inspection or reset the boiler.

9. Arrange a professional boiler check when it matters

Consider an independent boiler service or safety assessment before exchange if the appliance is old, records are missing, visible problems exist, the heating did not operate normally, or the cost of an early replacement would affect your offer. Be clear about what you want: a routine service, a safety check and a broader condition opinion are not necessarily identical scopes.

The engineer may need access, working gas and electricity, and enough time to run the system. Agree with the seller who will arrange and pay for the visit, and who receives the report. Verify the engineer on the official Gas Safe Register and check the qualifications shown on the back of their ID card.

10. Budget for the whole system, not just the white box

A replacement quote may need to include controls, system cleaning, filters, condensate work, flue changes, gas-pipe alterations, cylinder work or repairs to old radiators and valves. Moving a boiler or changing from a regular system to a combi can add significantly more work than a straightforward same-position replacement.

Do not rely on a generic online price to settle negotiations. Obtain a property-specific assessment if the likely cost is material to your purchase.

Questions to send the seller

• When was the boiler installed, and by whom?
• When was it last serviced? Please provide the record.
• Has it had leaks, pressure loss, fault codes or major parts replaced?
• Is any manufacturer warranty still active and transferable?
• Where are the user instructions and Building Regulations certificate?
• How are heating and hot water programmed?
• Do all radiators and hot outlets work normally?
• Where are the gas meter, main stopcock and heating isolation points?
• Have any rooms, bathrooms or radiators been added since installation?

On completion day

Take gas, electricity and water meter readings and photograph them. Check that the boiler has not been left showing a fault and that heating, hot water and frost protection are set sensibly for occupancy. Locate the stopcock and emergency contacts before unpacking hides everything.

Keep the manuals, certificates and service records together. Register any permitted change of warranty ownership promptly. If the property will be empty, do not simply switch off all protection during cold weather; follow the boiler and insurer’s instructions or obtain professional advice.

If you are selling

Organise the same information before buyers ask. Leave clear control instructions, manuals, recent service records and the location of meters and stop taps. Which? recommends leaving instructions for the boiler and alarm for the new owner. Honest records reduce uncertainty; do not describe a service as a guarantee that the appliance will remain fault-free.

Frequently asked questions

Does a home survey check the boiler?

A survey may note visible condition and basic operation, but it is not normally an internal gas-appliance inspection or service. Check the survey’s stated scope.

Must the seller service the boiler before completion?

There is no universal rule that every owner-occupier seller must provide a fresh service. You can request one or negotiate an independent inspection through the purchase process.

Is a landlord gas-safety certificate enough?

It records prescribed safety checks at that time. It does not replace your assessment of condition, service history, performance, warranty and future replacement risk.

Should I walk away if paperwork is missing?

Not automatically. Ask your conveyancer what evidence should exist and arrange technical assessment where needed. Missing records increase uncertainty, which should be understood before exchange.

Related boiler-help guides

• Boiler warranties explained: what keeps cover valid?
• Boiler service or gas-safety check: what is the difference?
• Combi, system or regular boiler: what is the difference?