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Last updated: 23rd April, 2024


How to Fix a Leaking Boiler

How to Fix a Leaking Boiler

Some possible reasons why your boiler might be leaking and how to fix them

It is likely that you have noticed your leaking boiler at the most inopportune time, and it is causing you a lot of stress. However, depending on the reason behind your boiler leaking, you may be able to get it fixed quickly and possibly even for free.

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You will know that you have issues with your boiler when you see water dripping from the boiler, or perhaps you have noticed a puddle of water underneath the appliance.

No matter what you have noticed when it comes to a leak in your boiler, it is not going to be good. It is very important that you seek help from an engineer as soon as you notice water leaking from your boiler. This is an issue that can cause some serious problems within your home, so getting it seen to early is one of the best ways to avoid this.

There are several different reasons why you may be experiencing a leaking boiler. If your boiler is old, covered in corrosion, and simply looks beyond repair, then it is time to replace it. You can often get a free quote from an engineer regarding the different boiler models they have and the cost of installation in your home.

Why Is My Boiler Leaking Water?

There are several different causes for a boiler leaking, and these can determine how much it will cost to be fixed or whether it can be fixed at all.

It is important that you call an engineer as soon as you notice your boiler leaking to reduce damage and ensure that there are no other issues, such as corrosion of other essential pipes and equipment.

Here are some of the most common issues when it comes to boilers leaking water:

Corrosion to Pipe Fittings

In most cases, the pipes that are immediately underneath your boiler are the main cause of leaking. Boiler leaks can often appear as a result of corrosion to the pipe underneath the device, which can happen over time or as a result of badly installed pipes.

Older boilers will experience leaking through this over time as the water in the device combined with the metallic debris will cause natural corrosion to the copper pipes. This will lead to small gaps in the pipework, which will cause water (and sometimes fuel) to start leaking out.

If you have a new boiler that has just been installed, then corrosion probably isn't the issue here but rather a poor installation job by the engineer. This doesn't necessarily mean that it is entirely their fault, but if this is the case, the company should send someone out as soon as possible to resolve the issue and make sure everything is secured within the boiler as it should be.

This is why it is vital that you use a reputable boiler and electrical company that has qualified engineers on hand for all services.

Too Much Boiler Pressure

Boiler leaks can also be caused by too much pressure in your boiler. It is possible that you don't really understand how boilers and pressure fit together, despite the fact you've heard the statement so many times, but don't worry, you're not the only one. You can also see our guide on what to do if your boiler is losing pressure.

Essentially, boilers (like many other devices - and people!) are not equipped to handle too much pressure. This is what can cause your boiler leaking water. Too much pressure in a boiler simply means that there is too much water being used, which can result in leaks.

If the pressure release valve (PRV) is too high on your boiler, then it will start to leak water as a way to alleviate this for itself.

Think about yourself when you feel under pressure - chances are it will be released through leaking water (aka. tears). This is essentially how your boiler operates, and leaking water can be a sign that the boiler pressure valve is too high, and it can't cope.

Sometimes the boiler pressure may be too high that internal parts of the boiler have failed or broken, which results in a leak and a broken boiler.

It is possible and very easy for you to check whether your boiler is being put under too much pressure, and you should do this as soon as you notice it leaking to avoid internal damage. Most boilers will have a pressure gauge on the front of the device (often located right next to the pressure valve).

There will be a green marking that indicates the right levels of pressure for your boiler model. If the dial is too far away from this, then you are dealing with an under-pressure leaking boiler. This can be treated by bleeding the system, which you can do without the help of a heating engineer, by turning the temperature valve on your radiators.

Corrosion and General Wear-

Boilers aren't made to last forever, so if you notice your boiler leaking, then it could be a sign that it needs to be replaced. Using an old gas boiler or similar model can actually be quite dangerous, especially when it starts leaking water and possibly fuel.

It is likely that over time the copper pipes of your boiler have been corroded, which will have caused holes. This is why the boiler leaking water is now an issue for you, as water is coming out through the pipes.

Make sure to call out an engineer to check out your boiler, even if it is an old gas boiler model, as they will be able to determine how much damage has been done and what repairs can be made. You will then want to get a quote to see the price of a new boiler and how much it will cost to replace your boiler. Then it's time to start saving!

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Faulty Heat Exchanger

The heat exchanger of your boiler is the most expensive part, so this can be one of the worst things to cause a boiler leaking water.

The heat exchanger can fail, crack, or come to other damage in old or low-quality boiler models, which can cause a lot of issues in your home. This is why it is very important for you to use a respected and qualified boiler company when getting a device installed, but this advice comes too late for those dealing with this issue right now.

It is not possible for you to determine whether you are having issues with the boiler heat exchanger unless you are a qualified engineer. This means you need to call out a gas safe registered engineer who can diagnose whether this is what's causing the boiler leaking water.

If it is a case of a faulty heat exchanger, then it can be replaced by a gas safe registered engineer. However, as this part costs so much, it may be better value for you to get a replacement boiler instead.

The engineer will be able to give you a quote for both the part and boiler replacement so you can determine which is the best value option.

Leaks from Internal Parts and Seals

Over time, it is possible for the seals and pump in your boiler to corrode over time. This can prevent them from working as well as they used to and will leave your boiler victim to internal damage, which can result in a safety issue for your home.

Internal leaks can cause a boiler leaking water at quite a rapid rate, so you will need to call an emergency engineer out if you notice this issue. They will be able to take a look at the internal parts of your boiler to see what is causing the water and fuel leak.

Is Boiler Leaking Water Dangerous?

In some cases, a boiler that has a leak can be dangerous, but this is only for older models. Your boiler will not explode or cause your house to fall down because it has a leak.

It is often just an inconvenience that can get in the way of your daily routine and will undoubtedly impact how happy you feel in your home.

However, this doesn't mean that this issue shouldn't be dealt with as quickly as possible.

This is especially the case for boilers that are connected to central heating, as it can cause this to stop working as well.

If you have old appliances in your home, then a leak can be a very dangerous matter, and you should get in contact with your boiler provider as soon as possible to prevent any further damage.

In most cases, those with older boilers will need their full central heating and water system replaced as this will be cheaper than getting certain parts mended.

Should I Hire An Engineer?

Even if you know how to fix a leaking boiler, that does not mean you can reliably do it yourself. Minor leaks are often easy enough to cover in the short-term, but major ones can become dangerous if you handle them incorrectly.

Remember that trained boiler engineers or experts are often taught exactly how to work with common boiler models. While you might have the instructions, they still have more experience with taking a boiler apart and putting it back together, something that can be incredibly useful even for basic repairs.

Older boilers, or boilers that heat up rapidly, often need a specialist’s touch. A leak is not inherently dangerous, but you can easily end up burning yourself with hot water or causing an even bigger leak that you ca not seal up properly.

The more dangerous and/or serious the leak is, the better it is to hire a specialist or engineer that can take care of it.

This becomes even more helpful if they are from the company that installed the boiler originally or even the company that manufactured that boiler model. They will be more familiar with how to take it apart, and may even know a faster way to seal the leak.

Should I Do It Myself?

In many situations, you can still repair a leak yourself as long as the damage is not anything too severe. You won't really be able to replace parts that need a gas safe registered engineer, but for small problems like cracked pipes, it is not impossible to handle every step on your own.

Remember that faulty installation can be one of the biggest causes of leaks, so you want to prevent it from happening again with your replacement parts. If you are even slightly unsure of what you are doing or do not know if you have installed a part correctly, then you might be better off calling an expert.

If you can’t identify the cause of a leaking boiler, you can’t tell how to fix a leaking boiler problem, so you should never jump into taking it apart without a plan. When there is no obvious cause of the issue, it is best to avoid doing it yourself, since you might make things worse by taking apart something that needed to stay together.

Should I Replace My Boiler?

It can be tempting to replace your boiler if you keep running into leaks despite fixing everything you can find, but do not do it straight away. It is entirely possible that your boiler is only leaking so much because of another part of the central heating system that you have not checked, like a damaged pipe.

Replacing your boiler should be a last-ditch option if you really can’t fix the issue and know that the boiler is responsible. In extreme circumstances, you might replace the boiler and a lot of the surrounding pipe system, but this can get increasingly expensive and disruptive to your normal life.

Only replace your boiler if you are sure that it will help prevent future problems, or if the boiler is damaged to the point that you can't rely on it anymore.

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Frequently Asked Questions

Can a Leaking Boiler Be Repaired?

Yes, a leaking boiler can often be repaired, depending on the cause and severity of the leak. Common issues like a faulty valve or a worn-out seal are relatively straightforward to fix. However, more serious problems, such as a crack in the boiler’s body, might require significant repairs or even a full replacement.

Why is Water Coming Out of the Bottom of My Boiler?

Water leaking from the bottom of your boiler can be caused by several issues, including pressure valve leaks, corrosion, pump seal failure, or loose/damaged pipe connections.

Is it Safe to Have Heating on if Boiler is Leaking?

It is generally not safe to continue using your boiler if it is leaking. A leak can lead to further damage to the boiler or your property and could be symptomatic of a more severe issue. It’s best to turn off the boiler and consult a professional immediately.

How Much Does it Cost to Fix a Leaking Boiler?

The cost to fix a leaking boiler can vary widely depending on the cause of the leak and the complexity of the repair. Minor issues might cost between £100 to £200, while more extensive repairs can exceed £500.

Will Turning Boiler Off Stop it Leaking?

Turning the boiler off won’t repair the leak, but it can help prevent further water damage and give you time to address the problem without additional complications. It is a good immediate response until a professional can assess the situation.

Is a Boiler Leak Covered by Insurance?

Whether a boiler leak is covered by insurance depends on your specific home insurance policy. Some policies include home emergency cover, which might cover the cost of repairs due to a leaking boiler. However, wear and tear or damage due to lack of maintenance often aren’t covered. Review your policy details or contact your insurer for clarification.

Who Do I Call If My Boiler is Leaking?

If your boiler is leaking, it is best to call a qualified heating engineer or plumber who is Gas Safe registered. These professionals can diagnose the source of the leak and make the necessary repairs safely and efficiently. Avoid trying to fix the leak yourself, as improper handling can exacerbate the problem or lead to dangerous situations.

Stephen Day profile photo
Article by
Stephen Day | Co-founder
Gas Safe registered and FGAS certified engineer with over 20 years experience in the heating and cooling industry.