Boiler Repair

Most of these faults share a few causes, so we test before replacing parts. Swapping parts on guesswork is how a small repair becomes an expensive one.

Most sealed systems run at typically 1 to 1.5 bar on the gauge when the heating is cold, rising a little when it is hot. Check your boiler manual for the right figure for your model. If the pressure keeps falling, water is escaping somewhere:

• A leak on the system: Look for drips at radiator valves, under the boiler and around exposed pipework. A hidden leak under a floor may need our leak detection and pipe repairs service.
• The pressure relief valve: A small copper pipe from the boiler usually runs outside. If it drips, the valve may be passing water, often because the expansion vessel has lost its charge.
• After bleeding radiators: Letting air out lowers the pressure, so top it up afterwards. Our radiator maintenance and repair service can deal with radiators that keep needing bleeding.

You can usually top up the pressure yourself using the filling loop, following the manufacturer's instructions, and close the valves fully afterwards. If you have to top it up more than once or twice, the fault needs finding.

Fault codes are set by each manufacturer, so the same code can mean different things on different boilers. Look up the code in your boiler's manual or on the manufacturer's website. Codes usually point to one of a few areas: ignition failure or flame loss, low water pressure, overheating, a fan or flue fault, or a sensor fault.

It is reasonable to reset the boiler once, as the manual describes. If the same code comes back, do not keep resetting it: repeated lockouts mean something is wrong, and resetting can hide a safety fault. Send us a photo of the display and the boiler's data badge, so the engineer can bring the likely parts.

• Pressure: Is the gauge in the normal range?
• Power: Is the boiler's fused spur switched on, and has a circuit tripped at the consumer unit?
• Controls: Is the thermostat set higher than the room temperature, and does the programmer show the heating as on? Flat batteries in a wireless thermostat are a common cause. Our thermostat and control maintenance and repair service deals with controls that have lost connection.
• Gas: Are your other gas appliances working, and does a prepayment meter have credit?
• In freezing weather: A frozen condensate pipe stops the boiler. Our emergency boiler services page explains how to thaw it safely.

Never remove the boiler casing yourself. It seals the combustion chamber, and only a Gas Safe registered engineer should open it.

Often, yes. A failed pump, fan, valve or sensor is a routine repair on most boilers. Replacement is worth considering when:

• the repair cost is high compared with the value of the boiler, for example a failed heat exchanger
• parts are no longer made or are hard to get
• the boiler has broken down repeatedly and the faults are getting more frequent
• it is an old non-condensing boiler, which uses noticeably more gas than a modern one

We give you an honest view, with the cost of the repair alongside the option of a boiler replacement, so you can decide.

1. 1

   Fault finding: we check the fault history, test the components and confirm the cause.

2. 2

   Explain and quote: we tell you what has failed and what the repair will cost before carrying it out.

3. 3

   Repair: we fit parts suited to your boiler. Where a part needs ordering, we make the boiler safe and return to fit it.

4. 4

   Test: gas tightness, combustion and the safety devices are checked before we leave.

5. 5

   Advise: if the fault was caused by sludge, we may recommend power flushing, or a central heating system maintenance visit if pumps or valves on the wider system are the problem.

If a boiler is unsafe to use, we explain why and, with your permission, turn it off until it is repaired.