Common Boiler Problems

May 03, 2023 | News

Common boiler problems

Boiler issues can be a major inconvenience, especially during colder seasons. In this guide, we cover the most common boiler problems and their solutions to help you maintain a warm and comfortable home.

Boiler Leaks

Boiler leaks are a common issue and should be treated as a serious concern. They can result from various factors:

  • Excessive boiler pressure
  • Corroded pipes or tanks
  • Faulty components
  • Leaks from seals

If you notice a leak, contact a qualified heating engineer immediately. Do not attempt to remove the boiler casing to find the source of the leak.

Hot Water but No Heating

Several reasons can cause hot water availability without central heating:

  • Combi boiler set to heat water only
  • Boiler set to turn on at unexpected times
  • Trapped air in radiators

Check the boiler display and bleed the radiators if needed. If the issue persists, consult a Gas Safe registered engineer to investigate and resolve the problem.

Low Boiler Pressure

Low boiler pressure can lead to cold radiators and insufficient hot water. Common reasons for low boiler pressure include:

  • Leaks in the system
  • Bleeding radiators

Repressurise the boiler by opening the filling loop, allowing water to re-enter the system.

Boiler Kettling

Boiler kettling occurs when water heats too quickly, causing steam and trapped air to produce a whistling sound. Causes of boiler kettling include:

  • Limescale build-up
  • Faulty components

A heating engineer can inspect the system, identify the cause, and recommend a solution, such as cleaning or replacing the affected parts.

Frozen Condensate Pipe

Frozen condensate pipes are common during colder months. To fix a frozen condensate pipe:

  1. Pour warm water onto the pipe to thaw it.

Boiler Not Responding to Thermostat

If your boiler is not responding to the thermostat:

  1. Ensure the thermostat temperature is set above the current room temperature.
  2. Replace the batteries in the thermostat or move it closer to the receiver.

If the issue persists, the thermostat may be faulty and need replacement.

No Heat or Hot Water

A lack of heat or hot water can result from several issues:

  • Disconnected power, gas, or water supply
  • Inappropriate boiler pressure
  • Piping issues or safety features

Contact a Gas Safe registered engineer to inspect the boiler and resolve the problem.

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Call our specialists on 020 8395 8616 or fill in our booking form.

Boiler Keeps Switching Off

A boiler may switch off due to:

  • Trapped air in the system
  • Low or high boiler pressure
  • Faulty thermostat
  • Debris and sludge buildup in pipes

An engineer can diagnose the cause and recommend a solution, which may involve replacing a faulty part or, in some cases, installing a new boiler.

Strange Boiler Noises

Various noises can originate from a boiler:

  • Gurgling noises: Indicative of trapped air in the system.
  • Drone noises: Usually caused by a faulty pump.
  • Humming noises: Often due to high water pressure from the mains.
  • Whooshing noises: Caused by debris blocking the air intake pipe or dust-clogged air filters.

Contact an engineer to investigate and resolve the issue as soon as possible.

Pilot Light Going Off

Older boilers may have a pilot light that needs to be constantly lit. However, the parts required for lighting the pilot switch can become faulty, such as the thermocouple. If your pilot light keeps turning off:

  1. Check if other gas appliances are working correctly. If not, the issue may be with the gas supply itself.
  2. If other gas appliances are functioning properly, contact a Gas Safe registered engineer to resolve the problem.

Modern boilers do not have pilot lights and therefore do not experience this issue.


Boilers can encounter a variety of problems, most of which should be addressed by a qualified boiler engineer. Regular maintenance and prompt attention to issues can help ensure a safe and efficient heating system. Remember, never attempt to replace any parts yourself; always consult a professional engineer to fix any problems safely and effectively.

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