Is your boiler broken? Here’s what to do next

There’s almost nothing worse than a broken boiler in the midst of winter. An inactive boiler usually means no heating and no hot showers, which may leave you feeling frustrated and cold.

When your boiler breaks down, it’s advised that you get a Gas Safe registered engineer to come out to the property and inspect the appliance for you, but there may be some simple fixes that you can do yourself at home, such as repressurising the boiler if the pressure has dropped too low.

If you smell gas, it could be a more serious problem than you think, and you should call the National Grid gas emergency line immediately on 0800 111 999.

If you don’t smell gas and are trying to work out why your boiler has broken down, our guide might help you to identify the reason why and how to fix it. Where the problem can’t be fixed yourself, you should call out a suitably qualified engineer to look at your boiler for you. 

Usually, it’s fairly obvious when your boiler has broken down because it either won’t be supplying heat to your radiators and taps or it won’t turn on at all. But sometimes, it’s not as easy to spot as this. Other signs that your boiler has broken down include:

• Funny noises, including banging, tapping, clicking or knocking
• A high energy bill
• A yellow or orange pilot light
• Pressure issues (either too high or too low)
• A leak in the pipes around the boiler
• If you notice any of these and your boiler is still working, it could be a sign that it’s about to break down. 

Once you’ve determined that your boiler has definitely broken down, it’s time to find out why. There are numerous reasons for this, as boilers contain lots of parts, but below, we’ve supplied the most common reasons so you can start investigating the problem. Some issues can be fixed by you, whereas others may require the assistance of a heating engineer.

• No power supply
• No gas supply
• No water supply
• Low or high pressure
• Frozen condensate pipe
• Faulty thermostat
• No pilot light
• Faulty or broken controls (diverter valve)

Electricity is essential for your boiler to work, despite the fact that they only use a little bit. This means that if there is an electricity supply issue, your boiler may not work as it should. Things that could cause a disruption to the power supply include a power cut, a tripped fuse in the main electrics box, a broken circuit board or even no credit in your account if you have a prepayment meter for your electricity supply. It could even be that someone has accidentally turned off the boiler’s electrical supply manually.

The easiest way to check if your boiler has an electricity supply is by looking at the digital or LCD display. If it’s on, then your boiler does have power, but it could be that something like a power cut has disrupted the boiler’s programming.

You can press reset on the boiler and leave it off for ten minutes. After this time has passed, switch the boiler on again and make sure that the date and time are correct, as well as your preferred programme. This should solve any issues to do with power cuts.

If the boiler is still not working, you should check your fuse box and make sure that all fuses are active. Also check that the boiler hasn’t accidentally been turned off at the main plug. Finally, you should make sure that you have enough credit on your prepayment meter. Once you’ve done all of these things and the boiler still seems to be broken, you may need to contact a Gas Safe registered engineer to take a look. It could be that the issue is coming from a broken circuit board and this issue cannot be fixed by you.

Your gas boiler has many safety features to ensure that the gas is being burned correctly and that the right amount of gas is being delivered to the appliance. If the gas isn’t being fully burned in the combustion chamber or too much gas is being fed into the boiler, it may shut down for safety reasons. A boiler could also have the opposite problem, where a blockage isn’t allowing enough gas in to be burned. Either way, gas supply is important for boilers but could be the reason why it’s not working properly.  

If you think you have an issue with your gas supply, the easiest thing to do is see if your other gas appliances are working, such as gas fires, ovens and hobs. You may also wish to speak to your neighbours to see if the supply issue is a local thing and not something to do with a problem in your home. This can also be done by checking your gas stopcock. If it’s switched on but you have no gas coming through, then it will likely be a supply problem.

Once you’ve checked all of these things to no avail, the final thing to check would be blockages that can occur in the gas valve. This would need to be checked by a Gas Safe registered engineer. 

We don’t often have issues with our water supply, but occasionally, this could be the cause of your boiler problems. When there’s no water being supplied into our homes, the boiler pressure will be very low and won’t turn on. 

You should check that your water supply is turned on and that you can get water from your taps. If not, there may be an issue in your area and you could contact your water provider for more information. Alternatively, check their website as this can sometimes show supply problems. 

It’s imperative that the water pressure in your heating system is at the right level for your boiler. This is usually between 1 and 1.5 bar of pressure. The gauge on the front of the boiler will tell you if it’s at the right level.

When the boiler pressure is too low, the boiler will struggle to ignite at all or may not even bother. You can tell when the pressure is too low by checking the gauge on the front of the boiler. There’s usually a needle that should sit between 1 and 1.5 bar of pressure (also sometimes marked out with a green colour). If the needle is in the red zone below this, then there’s not enough water in the system for the boiler to work properly. Low boiler pressure can also show up as a fault code on the screen.

It can also be a problem if the water pressure is too high. This can be caused by too much water in the system, which again would show on the pressure gauge as above 2 bar.

Pressure problems usually stem from a leak but may also suggest that there are problems with the expansion vessel, pressure relief valve, heat exchanger or filling loop.

For low pressure, it’s a good idea to repressurise the boiler, allowing water into the system until the needle is in the green zone on the gauge. Keep an eye on it for the next few days to make sure it doesn’t drop again. If it does, there could be a leak somewhere within the system.

For high pressure, you should let some water out of the system. Read our guide on high boiler pressure to find out how to do this.

If you believe the problem is caused by a leak or issues with any of the parts we’ve mentioned above, you should call a suitably qualified heating engineer. 

Frozen condensate pipes are fairly common in winter when temperatures go below zero, but they can wreak havoc with your heating system. The condensate pipe allows water vapour and condensate to exit your heating system, and it can freeze at the point where the pipe leaves your home. When this happens, your boiler will shut down as a safety precaution.

Locate your condensate pipe and check for ice or icicles. If you can see some frost or ice buildup, a good temporary solution is to pour warm water (not hot water) onto the pipe. Then, reset your boiler to see if the fault code goes away.

This DIY approach does work, but the ice can return when the cold weather persists, so it may be better to call out a Gas Safe engineer to take a closer look.

We’ve been through quite a few errors and problems now, but if it still isn’t working, it could be due to your thermostat. A thermostat will tell a boiler to heat your home when it drops below a certain temperature and to stop heating when a set temperature has been reached. For this reason, it may not be your boiler that’s broken at all, but an error with the thermostat. It may be that it’s not communicating properly with the boiler, that the clock is set incorrectly and that it’s set below the room temperature (in which case, it thinks your home doesn’t need to be heated and won’t nudge the boiler to come on). 

Locate your thermostat and check that it’s on, that the thermostat is set above the current room temperature (20 ℃ is usually a comfortable heat) and that the clock is set to the right time. You may also want to check that the thermostat can speak to the boiler. In wireless systems, this is done with a receiver that is located near your boiler, so check that this device is working too.

Modern boilers don’t tend to have pilot lights and are instead lit by an electric ignitor. But if you have an older boiler, the pilot light needs to be lit so that it can burn the gas needed for central heating and hot water. There is usually a small window in the boiler casing so that you can see inside and check that the pilot light is there. It can occasionally go out, particularly if it’s draughty. 

If you cannot see a pilot light, you should use your boiler manual to relight it. When this cannot be done, you should call a Gas Safe registered engineer out to check the boiler over for you. It could be that the flame is going out due to lack of oxygen in the chamber.

A diverter valve allows your boiler to control where the heated water goes - some will need to be directed to your radiators to heat the property but some will also need to go to a hot water tank to provide you with hot water for baths, showers and more. When this diverter valve is faulty or not working, you may find that your radiators are heating up but that you have no hot water. 

Unfortunately, there is no way of checking your diverter valve yourself. Instead, you will need to contact a suitably qualified engineer to look over the boiler for you and determine why it’s broken. 

When you rent your home, broken boilers are considered to be an emergency and so under English and Welsh law, your landlord should aim to fix the problem in 24 hours, or at least organise an emergency heating engineer to take a look at the appliance.

If you have boiler cover or insurance, emergency call outs may be covered, meaning you don’t have to pay a thing. 

Within this guide, we’ve mentioned ‘Gas Safe engineers’ a few times. An engineer should only look at your boiler if they are registered with Gas Safe. This means that they’re approved and fully qualified engineers with the correct accreditations. But how do you find a Gas Safe approved engineer?

The easiest way to find someone to fix your boiler is by checking the Gas Safe register. Simply enter your postcode and it will provide you details of an engineer local to you. Alternatively, you can find a Viessmann-trained installer, which may be ideal if you have a Viessmann boiler.

You can also contact a plumber to work on your boiler, but you must check that they are on the Gas Safe register. Most plumbers work with water-based devices, such as toilets, showers, pipes, etc. In order to work on a gas boiler, they must be on the register. This is where there can be some confusion around who to call.