Your guide to the top 10 most common boiler problems and solutions.

Whether you’ve got a noisy boiler, pressure problems or the condensate pipe has stopped working, we’ve got you covered.

Boiler problems.

What are the most common boiler problems?

  1. Boiler leaking or dripping water.

  2. Low boiler pressure.

  3. Boiler making banging noises.

  4. Hot water but no heating.

  5. No heat or hot water.

  6. Boiler pilot light keeps going out.

  7. Boiler kettling.

  8. Boiler keeps switching off.

  9. Frozen condensate pipe.

  10. Boiler not responding to the thermostat.

Some of these can be resolved by you, however most will need a qualified gas safe boiler engineer. We’ll go through each one and what the best course of action is to get your boiler issues sorted.

It’s also important to organise a regular boiler service to help avoid these problems.

1. How to fix boiler leaking or dripping water?

Boiler leaks or drips are one of the more common issues that you may face. They can cause water damage to your home and can also cause electrical components in and around your boiler to malfunction or break.

Boiler leaks are normally caused by:

  • Corroded pipes or tanks.

  • Excessive boiler pressure.

  • Leaky seals.

  • A faulty component.

If you do have a boiler leak then you should call a qualified Gas Safe heating engineer. They may recommend that you switch off the water to your home to prevent further leaks until they’re able to get there.

Don’t attempt to remove the boiler casing to find the source of the boiler water leak yourself.

2. Fixing low boiler pressure.

The signs that you have low boiler pressure are a lack of hot water and cold radiators. You can tell if you have low boiler pressure by looking at the display panel on your boiler. The boiler pressure level should normally be around 1-1.5 bars, so if it’s less than that then you could be dealing with low boiler pressure.

The pressure in your boiler can drop due to:

You can fix low boiler pressure by repressurising your boiler. To repressurise your boiler:

  • Turn off your boiler and allow your central heating system time to cool down.

  • If your boiler has a filling loop you can repressurise the boiler by opening the valves and allowing water to enter from the mains.

  • If your boiler uses a filling key you’ll need to turn the key to allow water to flow into the system.

If your boiler doesn’t repressurise then there could be a bigger problem such as a water leak or a fault with your pressure release valve. We recommend calling a Gas Safe heating engineer out to inspect your boiler.

Don’t keep trying to repressurise your boiler as this can damage it.

3. Why is my boiler making banging noises?

Hearing banging noises coming from your boiler? There a number of reasons why you have a noisy boiler:

  • Low boiler pressure.

  • Trapped air.

  • Blockages such as limescale or sludge build-up.

  • Faulty pump.

Low boiler pressure.

This can cause a humming noise and means that the boiler pressure is not at the ideal level. Check your boiler’s pressure gauge and repressurise if required.

Trapped air.

Trapped air in your central heating system can cause a gurgling noise. It’s recommended you bleed your radiators to remove the trapped air.


If you hear a whooshing noise then you may have a blockage in your heating system. You may need to have your heating system flushed by a trained expert. A clogged-up heating system can increase the pressure and lead to a boiler breakdown.

Faulty pump.

If your boiler’s pump is faulty then you may hear a droning noise. You’ll need to get the pump resealed or replaced by a Gas Safe engineer.

4. Why have I got hot water but no heating?

Have you got hot water coming from the taps but your radiator is as cold as ice? There are a couple of ways you can get your central heating working again.

  • There may be trapped air in the radiators. If you bleed the radiators this may solve the problem.

  • Your boiler may be set so that the heating is coming on at the wrong time. For example if you had a power cut and everything was reset. Check your boiler display/thermostat to see when it’s coming on and to what temperature.

  • If you have a combi boiler you may have set it to heat water rather than both water and central heating. Check your boiler display/thermostat.

  • Your boiler or heating system may be faulty. In that case you’ll need a gas safe engineer to investigate and fix the issue.

5. No heat or hot water?

If you’ve been left with no heating or hot water then you’ll most likely need an engineer to come resolve the issue. Some of the issues you could be facing are:

  • Low or high boiler pressure. The heating system will turn itself off automatically if this happens.

  • Frozen condensate pipes or an airlock caused by trapped vapour/air.

  • Your boiler has become disconnected from the power, gas or water supply.

  • Possible faulty components inside the boiler.

6. Why does my boiler pilot light keep going out?

If your boiler is an older model then you may have a pilot light. This needs to be constantly lit to light the larger boiler burner that heats the water in your home.

If the pilot keeps turning off, first check that other gas appliances are working correctly. If they aren’t then it may be an issue with your gas supply.

If your other gas appliances are working correctly then you’ll need to call a Gas Safe engineer to fix your pilot light.

New boilers don’t come with a pilot light.

7. Is boiler kettling dangerous?

The boiler kettling noise is when water is heated too quickly, causing steam to be generated within your heating system and air to become trapped. The trapped air gives off a whistling sound which sounds like a boiling kettle.

Boiler kettling can be caused by:

  • A faulty component on your boiler.

  • Limescale build-up which slows the flow of water in the system.

  • Boiler pressure issues.

How to fix boiler kettling.

You’ll need to get a professional to identify the cause. If the problem is boiler pressure then you may be able to repressurise the boiler yourself.

8. Why does my boiler keep switching on and off frequently?

Like many of the boiler problems already mentioned, your boiler may be switching on and off due to:

  • High boiler pressure.

  • Low boiler pressure.

  • Trapped air.

  • Blockages.

  • Faulty thermostat.

You may be able fix the boiler problems by repressuring your boiler, however an engineer may be required.

9. Sorting out a frozen condensate pipe.

If you have a condensing boiler then you’ll have a boiler condensate pipe that takes the waste water produced as part of the condensing process outside of your home. If the temperature drops too low over the winter months, then the condensate pipe can become frozen which will shut down your boiler.

How do I know my condensate pipe is frozen?

You’ll normally see an error code on your boiler which will tell you the pipe is frozen. You might also hear a gurgling noise come from the boiler.

How do I find a condensate pipe?

The condensate pipe usually looks like a white overflow pipe, similar to what you’d find on your washing machine or sink waste pipe. It’ll be located on the external wall outside from where your boiler is.

How do I defrost a condensate pipe?

You can thaw a frozen condensate pipe by pouring warm water onto it. It may also be advisable to wrap your condensate pipe in pipe insulation (also called pipe lagging) so that there is less risk of it freezing.

10. Boiler not responding to the thermostat.

Sometimes your boiler and thermostat stop communicating, which causes your heating to come on at the wrong time or the temperature to be too hot or cold.

How to fix a boiler thermostat.

If you don’t think your boiler is responding to your thermostat then you may need to replace the batteries or move it closer. If that doesn’t fix it then you may need a new thermostat.

Get warm and cosy and save up to £475 on your annual gas bill^.

Plus if you’re an E.ON Next customer save £150 when you buy a boiler through E.ON. T&Cs apply.

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^An average household could save up to £475 on their annual gas bill. Savings information for boilers in the UK provided by the Energy Saving Trust, based on a detached house with a boiler rating of G.