The Top 10 Most Common Boiler Problems


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In this article we explore the top 10 most common boiler problems.

Most of us don’t give our gas boilers a second thought unless they break down or cause problems with the hot water or heating. Even though they are an essential appliance in our homes.

If there’s a problem with your boiler, it can affect your cooking, washing, showers and the warmth of your home.

There’s nothing worse than a freezing home in winter. It’s the busiest time of the year for gas engineers, so you may have to wait a while for help.

A boiler has many small working parts, some of which can malfunction due to a variety of reasons. Here are the top ten most common boiler problems.

Table of contents:

    1. Leaking

    What Happens?

    You may notice drips from your boiler or a flow of water. Basically, a leaking boiler means that an internal component such as a seal or valve is broken.

    This could then cause electric components within the boiler to short circuit or it may lead to corrosion within the boiler.

    Leaking is one of the most common boiler problems.

    What Next?

    The first thing to do is to isolate your water supply to the boiler and turn off the electrics to the boiler. Then, if it’s leaking a lot, use a container or towel to stem the flow of water.

    You should then contact a qualified gas engineer to investigate the source of the leak. They will be able to fix the problems, or it’s possible that you may need a new boiler.

    2. Frozen Pipes

    What Happens?

    Your boiler has a condensate pipe which is outside your house. This pipe carries the condensate from your boiler to the outside drain. It usually looks like a white PVC-U pipe.

    In cold weather, the pipe can freeze, causing your boiler to stop working properly. A frozen pipe means the condensate can’t get out and may revert back to your boiler causing it to eventually break down.

    Hence it’s worth insulating the pipe as soon as you can so the problem doesn’t happen again

    What Next?

    Heat some water in your kettle, but make sure it isn’t boiling, or you might crack the pipe. Then slowly pour the hot water over the frozen section. Or, try placing a hot water bottle on it.

    3. Cold Radiators

    What Happens?

    Perhaps your radiators have cold spots. The hot water from your boiler is not reaching them effectively. Over the years, a certain amount of sludge and pressure builds up in every central heating system.

    What Next?

    You need to bleed the radiators. Which means adjusting the valves on all of the radiators in your home and releasing some of the pressure.

    You will need a small container or towel for this to catch any sludge or drips that come out from the valve as you are adjusting it.

    If your radiators are still cold after bleeding, then you may need an engineer to flush the entire system.

    4. Strange Noises

    What Happens?

    The boiler is making weird noises, and the type of sound it makes will identify the fault. For example, a banging sound will probably indicate that the pipework or an internal component has come loose.

    Whereas a buzzing noise could mean that an electrical part is malfunctioning. There are other sounds like clanking, humming and gurgling.

    Ultimately, your boiler is supposed to run quietly, so any loud sounds indicate a problem

    What Next?

    A noisy boiler means that it needs attention as soon as possible. You could try bleeding the radiators or checking the pipework. If the noise continues, you should seek expert help.

    5. Low Boiler Pressure

    What Happens?

    Your boiler has a pressure gauge on the front of it, so you will either see a needle or a bar on a screen. If the needle or bar is below 1, then the pressure is too low.

    Ideally, it should point between 1 and 2. A sudden drop in pressure indicates a bigger problem.

    What Next?

    If it’s low, this could mean a water leak or that your radiators need bleeding. You can increase the boiler pressure yourself, follow directions in your boiler manual, but if you’d rather not, then ask an expert to help.

    6. High Boiler Pressure

    What Happens?

    If the pressure is too high, most boilers have a safety device which shuts it down if this is the case. When the pressure gauge is showing above two bars or pointing to red, the pressure is too high.

    What Next?

    You can reduce the pressure yourself by switching off the boiler and waiting for it to cool down. Make sure the filling loop is tightly closed, and bleed the radiators to release trapped air. Then check the pressure again.

    7. No Heating

    What Happens?

    The hot water is working but there’s no heating. In this case, start by checking your thermostat. Your thermostat controls what time your heating comes on, so maybe it’s a problem with the settings.

    If not, then check the pressure gauge on your boiler. If the pressure is too low, the central heating won’t work properly.

    What Next?

    You can adjust the pressure yourself by switching off the boiler and waiting for it to cool down, then turning both the filling loop handles.

    You don’t want to raise the pressure too high, so you will need to see the gauge at all times. If unsure of the process, then ask an expert to help.

    8. No Heating or Hot Water

    What Happens?

    If you boiler is still running but you’re not getting any heat or hot water then you might see an error code. It could be a number of issues.

    Try checking the thermostat settings again, as well as the condensate pipe outside. If all OK, check for low or high pressure on the gauge.

    Failing this, there could be a problem with the fuel supply. Maybe you have run out of oil if you have an oil boiler. Or there’s an issue with the mains gas supply.

    What Next?

    If you’ve made all your checks and it’s still not working, call a gas engineer for advice.

    9. Pilot Light Keeps Switching Off

    What Happens?

    Over time, your boiler collects dirt and dust. Sometimes this causes working parts to malfunction. A faulty pilot light may indicate a problem with the thermocouple.

    The thermocouple is an electrical sensor which monitors the temperature. It’s usually found to the right of the pilot light.

    What Next?

    It is possible to change the thermocouple yourself, you can remove it, let it cool down, then give it a clean and put it back. However, if unsure, call an engineer to help you.

    10. Ongoing Problems

    What Happens?

    If you find that you are calling out an engineer quite often, then your boiler could be at the end of its lifespan. An A rated boiler which has annual maintenance should last up to 15 years.

    If your boiler is older that this and regular breaks down, it’s most likely that you need to replace your boiler.

    What Next?

    Do some research into what type of boiler you would like next. The cost depends on several elements including warranties, the model and even who installs it.

    Sometimes a local engineer can be cheaper than a national brand. Compare a few quotes first.


    In summary, a gas boiler is an essential part of your home that needs to function correctly for you to receive hot water and heating.

    As you can see, there are a number of reasons why a boiler can go wrong & cause problems, and some of these you can even fix yourself.

    However, if you need some expert advice, then call a gas safety engineer who can help you.