There are many reasons why you may be having issues with your boiler and you may not know whether you need to call out a heating engineer to take a look or not. Some common issues that we get called out for are often not with the boiler itself and can be down to other areas of the heating system. Here are some of the most common problems and our recommendations of what you should do.

Your boiler is likely to be a gas appliance and therefore should only be repaired by a Gas Safe registered heating engineer. Do not try and repair a gas appliance yourself.

Which DIY jobs can you tackle yourself?

Radiator faults

Cold patches and other problems are usually caused by a build-up of air or sludge inside of radiators, this can cause heat to be distributed unequally. Cold patches in different areas can indicate different kinds of issues, find out how you can fix your cold spots here.

A great deal of radiator issues can be resolved by bleeding the radiator, a simple task that you can undertake by yourself.

When the problem is not related to the balance or bleeding, then chances are built-up sludge is preventing the flow of hot water to the radiators. Don’t try cleaning the sludge by yourself. Call a heating engineer. They use chemical flushing to clean the system and remove the sludge.

Boiler won’t turn on

If your boiler won’t turn on, the first thing you should do is check other appliances and power supplies in your home to see if they are working. If they are, check your fuse box to see if any switches have failed or tripped. If you still cannot find the cause, we recommend getting in touch with a trained engineer.

If your boiler is turning on but keeps going off, the pressure could be low or there could be a blockage that is inhibiting the system. Check your system’s pressure gauge and repressurise the boiler if it is set below 1. Alternatively, contact a Gas Safe registered engineer.
Boiler not responding to thermostat
Have the clocks gone backwards or forwards recently? If so, you should ensure that the device is in line with the new time. If your boiler is completely failing to respond to your thermostat, the controls may be broken or old. However, there are a few checks that you should do before concluding that it is completely irreparable.

For example, try replacing the batteries. You could also try positioning the device closer to the boiler and check for any interference that could be causing an issue. If the problem with your thermostat persists, take a look at the instructions booklet for advice or contact the manufacturer for help.

Problems you should call in a professional for


A boiler can leak water because of a variety of issues. To determine the cause, it’s important to learn where the water is leaking from. Usually, it happens when an internal component of the boiler such as a pressure valve or a pump seal is broken. If the leak is because of the pressure valve that means the boiler pressure was high. On the other hand, if it’s coming from the pump seal that means it needs replacement.

Sometimes, the boiler is leaking from around the tank or pipes. This happens because of corrosion or improper fitting.
Low boiler pressure
You can usually identify if your boiler’s pressure is too low by taking a look at its built-in pressure gauge. Ideally, your boiler’s pressure should be set at the 1.5 bar. If it is below 1, your boiler will not be able to function properly.

Low boiler pressure can be caused by issues such as a system leak, recently bled radiators or a failed component or seal. To help identify the issue, you could firstly look for visible signs of a leak, but you should not attempt to remove any casings from the boiler. If you discover a leak, we recommend that you contact a Gas Safe registered engineer. If you do not locate a leak, you could try repressurising your boiler if you feel comfortable doing so.

No heating or hot water

There could be many possible causes. A broken diaphragm, valve or thermostat. A good place to start is checking the thermostat. If the problem isn’t the thermostat but a part is broken (valve, airlock or diaphragm), then simply replace them and your boiler will start working again.

To determine whether this issue is caused by low pressure, you should check your pressure gauge to see if it is below 1. If it is, it may need repressurising. If the intermittent heating and hot water is caused by an issue with your thermostat, check the device’s manufacturer guide for a possible solution – if none can be found, we recommend that you contact your manufacturer for help.

If none of these suggestions help, we advise that you get in touch with a trained engineer as issues such as a broken motorised valve or faulty diaphragm will require a professional.

Unusual Boiler Noise

It’s normal for the boiler to produce a low hum. However, if it is making a louder and unusual sound, then this could be a sign of a serious problem.

You will hear the boiler either whistle or gurgle. The boiler whistles when air is trapped in the pipes or the boiler itself. Bleeding the radiators solves this issue. If the boiler is gurgling, it means there is a frozen pipe somewhere that is disrupting the water flow. You might have to call a gas safe engineer to locate the frozen pipe and deal with the problem. That should fix the noise.