Can a boiler explode?

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Can a boiler explode from over heating or high pressure?

Yes, a boiler can explode, but it is very rare that they do. Most modern boilers are built to withstand reasonably high pressure, but if this gets too much then an explosion could happen.

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Whilst this is more common in older boilers which there aren’t that many of now, most new boilers have fail-safes like a pressure relief valve or will just stop working if the pressure gets too high. This is called boiler failure.

What can cause a boiler explosion?

If you are seriously worried about a potential boiler explosion, then either turn it off or call a Gas Safe registered engineer right away. High boiler pressure, overheating or loud noises are all signs that something isn’t right that can lead to your boiler going bang.

This is usually caused by a faulty boiler or a bad installation. Potentially your pressure relief valve may be blocked or too tight or a wiring error which is stopping the boiler from realising pressure is building.

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What are the signs that your boiler is going to explode?

Here are some tell-tale signs that a boiler is on the verge of exploding. The following different problems are all potential issues that could lead to a boiler explosion or catastrophic failure.

All of the following symptoms can lead to an exploding boiler in a worst-case scenario but they can also be other issues too which if you catch nice and early can save you a hefty bill or any damage to your home.

If you think your boiler could explode, we strongly suggest that you get a new one.

Too much pressure in your boiler

The normal running internal pressure of a combi boiler is around 1.5 bar or 21psi. If there is too much pressure in your boiler, you can release it by bleeding your radiators, but your central heating system must be cold so you don’t get burnt. If you try to do this when hot and under high steam pressure, you could cause serious injury to yourself.


Overheating or excessive heat when you go near your boiler

pressure gauge

You should be able to touch your boiler at any point. If your boiler is extremely hot or you can’t touch your boiler, then it needs to stop and shut down right away. This is when internal pressure builds up and your boiler is not working properly

Your boiler smells like rotten eggs

If your boiler is leaking or central heating water smells funny, then this is a tell-tale sign that something is wrong and parts could be compromised causing a build-up of sludge or sediment. This then builds pressure and could cause boiler explosions. 

Excessive noise coming from the boiler

If your boiler is making really loud noises, this could be high pressure in your boiler building up or broken safety valves which can make your boiler explode. Boiler kettling is another common issue too.

The operating pressure of your boiler keeps rising

All combi boilers have an operating pressure gauge. If your boiler pressure gauge rises higher than 3 bar continuously, then you have excessive pressure and this excess pressure needs to be released. This is the job of pressure relief valves, but if this is not working properly, you may need to bleed your radiators. Low boiler pressure is less of an issue

Broken pressure relief valve

pressure releif valve

Boiler failures can often be caused by a broken or stuck safety valve. Under normal operation, if your safety valve is working then if your boiler is creating pressure, it will

Is your boiler overheating?

If your boiler is overheating, you should call a heating engineer right away. A boiler that is getting too hot is an emergency and needs to be fixed right away as this could cause the explosion you are worried about. Letting your boiler cool down is the most important thing to do in this situation. 

What to do if your boiler is getting too hot?

inside combi boiler

If you think it is safe to do so, you should turn off your boiler at the mains, and if you know how to or if it is possible, stop the water supply. This will, in turn, stop any build-up of pressure and prevent your boiler from exploding. If you have managed to do this, you need to let your boiler cool down. 

Let the boiler cool down gradually

Do not switch your boiler back on until a Gas Safe registered heating engineer has taken a look at your boiler as there may still be excess pressure. It is highly likely that you will need a new boiler. Find out how much a new boiler cost now by getting a quote online. 

Back boiler explosion – What to look out for

Back boilers are different from combi boilers as you can’t actually see or hear everything that is going on as well as a new modern boiler that is in a cupboard. Back boilers are generally older too so are much more susceptible to things going wrong.

A back boiler explosion could be disastrous but ensure that if it is making loud noises or giving out excessive heat you get someone to look at your back boiler fire right away.

What to do if your boiler explodes?

If your boiler explodes, this is an emergency and you will need to call the gas emergency helpline on 0800 111 999. If it is dangerous or on fire, you must call 999 and ask for the fire service. Boiler explosions are serious and need fixing right away. There is also the risk of carbon monoxide poisoning or fuel explosion.

If you believe that there is no immediate threat and the boiler is safe, you can call a gas Safe registered emergency heating engineer to come out as soon as possible. They will condemn the boiler and shut off the gas. You will then need to make arrangements for a replacement boiler installation.

What to do to prevent boiler explosions

Whilst boiler explosions are not that common anymore, we strongly recommend that you do the following things to make sure. Whilst a modern gas boiler can withstand excessive pressure, all the following checks and proper maintenance tips are great for keeping your gas boiler in tip-top condition for as long as possible. 

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  • Ensure that you get an annual service of your boiler every year. This typically costs around £90 and can make sure that your boiler is at the right pressure and working correctly. This is much cheaper than paying for repairs or mechanical failure after a boiler explosion.
  • Physically check the boiler pressure yourself periodically. On most combi boilers in the UK, there is an easy-to-read pressure gauge. This should be around 1.5 bar. Some of the best combi boilers can check and amend the pressure themselves. 
  • If you are replacing a boiler, then you must ensure that you use a Gas Safe registered installer. This lessens the chance of a bad installation which is one of the more likely reasons for boiler explosions.

Replacing an old boiler can prevent boiler explosions

If you have got an old combi boiler then it may be time to get a new one if you think that your old one is dangerous. As we say such explosions are rare, and most boilers can protect themselves.

You can ensure that you get a top-of-the-range boiler with 1st class boiler replacement by getting a boiler quote online now with Boiler Central. If your boiler is completely broken, you can even get emergency boiler installation and get a new boiler fitted fast in under 24 hours.

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