1. No Hot Water or Heating
The most obvious boiler problem – and often one of the most straightforward to fix. Common causes include a tripped circuit breaker, a frozen condensate pipe (in cold weather), low boiler pressure, or a faulty thermostat or timer. Before calling an engineer, check that the pressure gauge reads between 1 and 1.5 bar and that your timer/programmer is set correctly.
2. Low Boiler Pressure
Most modern condensing boilers need a pressure between 1 and 1.5 bar to operate. If the gauge shows below 1, you can repressurise the boiler using the filling loop (usually a grey braided hose connecting two pipes near the boiler). If the pressure keeps dropping, you likely have a slow leak somewhere in the system – call an engineer.
3. Boiler Losing Pressure Repeatedly
A boiler that needs repressurising more than once a month is a sign of an underlying issue: a failing pressure relief valve, a faulty expansion vessel, or a small leak in the pipework or radiators. Don't ignore it – it will get worse.
4. Strange Noises – Banging, Kettling, or Whistling
A kettling noise (similar to a boiling kettle) is caused by limescale or sludge restricting water flow through the heat exchanger. This is common in hard water areas like Surrey and West Sussex. Banging noises can indicate trapped air or a failing pump. Whistling often points to a restricted flow. All of these warrant an engineer visit.
5. Boiler Keeps Switching Off
A boiler that shuts down and requires frequent resets is in a fault or "lockout" state. This can be caused by low pressure, a faulty thermostat, a blocked condensate pipe, or an internal fault. Check the pressure first, then call an engineer if the fault recurs after resetting.
6. Pilot Light Going Out
Older boilers with a pilot light may see it extinguish due to a faulty thermocouple (the safety device that detects whether the pilot is lit), a draught, or a gas supply issue. Modern condensing boilers use electronic ignition rather than a pilot light, so this is less common in newer installations.
7. Radiators Not Getting Hot
If all your radiators are cold, the problem is usually the boiler or pump. If only some are cold, the issue is likely either trapped air (bleed the radiator) or sludge build-up causing blockages. Cold radiators at the top are usually air; cold at the bottom is usually sludge.
8. Boiler Leaking Water
Water leaking from or near your boiler should never be ignored. Common culprits are a faulty pressure relief valve (discharging because pressure is too high), a corroded heat exchanger, or a failed pump seal. Turn off the water supply to the boiler and call an engineer promptly.
9. Frozen Condensate Pipe
All modern condensing boilers have a condensate pipe that carries acidic water to a drain. In cold weather, this pipe (usually plastic and running down an outside wall) can freeze, causing the boiler to lock out with an error code. You can often thaw it yourself using warm (not boiling) water poured over the frozen section.
10. Error Codes on the Display
Modern boilers display error or fault codes when they detect a problem. The meaning of these codes varies by manufacturer – your boiler manual will list them, and most are also available online. Common codes relate to ignition failure, fan faults, pressure issues, and sensor failures. If you're unsure what a code means, call us and we'll help you interpret it.
When Should I Call an Engineer?
If you've checked the basics (pressure, timer settings, condensate pipe) and the problem persists after a single reset, call a Gas Safe engineer. Never attempt to open the boiler casing yourself or interfere with gas components – this is illegal and dangerous. Call Whitebox Heating on 01293 000 000 for fast, local assistance.