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Last Updated on January 22, 2021

Boiler Leaking Water – What To Do? 6 Causes & Fixes For Dripping Pipes

Zac Houghton

Zac Houghton

Construction expert and founder of Loftera.

If your boiler is leaking water, you want to attend to it as a matter of urgency.

Failure to do so could easily result in mould, rust and corrosion in your home. What can start out as a seemingly small issue, can quickly develop into a major one. So don’t wait, get your leaking boiler fixed as soon as possible.

Hopefully, by the time you have read this post, you’ll be better informed into why your boiler is leaking water, the steps to take to fix it, and how much it will cost to replace.

Let’s begin with the basics and help you to understand why your boiler is leaking water from the bottom or indeed the overflow pipe.

boiler leaking water

Table of Contents

Why Is My Boiler Leaking?

There are several factors that can be the root cause of a leaking boiler, and it only takes one of them for your issue to escalate. Of course, more than one of these factors can make the job of repairing your boiler more difficult, so it is vital that you understand the possible causes.


While combi boilers tend to be designed to handle high pressure problems, conventional or system boilers are not necessarily fitted with this capability.

In essence, the boiler needs to relieve any excess pressure to stop it from breaking down. If the pressure is too high, the pressure release valve will discharge the excess water. Failure to do so will result in the boiler to fail.


Where water is involved, corrosion is often an unavoidable inevitability. However, corrosion in your pipes or tank to your boiler can cause serious issues. They can begin to weaken, in turn allowing water to escape.

If just one small part of the tank or pipe is suffering from corrosion, you may be able to replace that particular element. However, if the corrosion is more serious, and has spread further than that, you may be best investing in a new boiler. Our recent blog discusses new boiler costs and which option is best for you.


When a boiler reaches a temperature that is considered to be too high, leaks can then occur. All boilers are fitted with what is known as a temperature control valve. This keeps an eye on the temperature of the water in the boiler itself, and is designed to prevent it from becoming too high.

It goes without saying that any checks on this issue should be done so with extreme caution. If the water temperature is too high, the leaking water will be close to boiling, and can cause injury or burns if not careful.

Manual Error

You’d like to think that the professional responsible for fitting your boiler has done so to the best of the ability. Even if that is the case, human error sometimes cannot be helped. If pipes aren’t fitted correctly, it is an inevitability that water will leak from your boiler.

Only go with a fully qualified engineer when fitting a new boiler, and be sure to ask for the checklist of their work so you can be sure that all the required steps have been taken.

Loose Joints

Unfortunately, pipes and joints do tend to become loose over time. It is the same on any fitting of this kind, not just boilers. However, the difference with loose joints in boilers is that they usually occur due to the very nature of the appliance itself. When heated, the pipes will expand and then contract upon cooling. Over time, this will result in the fittings become loose. They will need to be tightened from time to time to make sure that this doesn’t become an issue.

Pump Seals

In essence, a boiler pump is designed to pump water around your home. Imagine then, that the pump seals aren’t correctly installed. Doesn’t sound great, does it? You’ll want to be sure that the pumps are sealed as tightly as possible, or they too may need replacing.

Worn Out Over Time

Boilers, just like us humans, suffer from wear and tear. Ever hear somebody claim they aren’t the same person they were ten years ago? The same can be said for your boiler, so treat it with the care that it deserves.

If your boiler is ten years old or more, the time may well have come to replace it. Sure, there is an initial cost in doing that, but it will save you money on bills due to the increases energy efficiency inside your property.

Steps To Take To Avoid More Water Coming Out Of Your Boiler

The main step that you should take is to contact an engineer to fix the problem for you.

However, in the meantime, there are measures that you can take to prevent even more water from leaking from your boiler and into your property.

Have a good check around the area to ensure that all of the leaks in question have been located, and then do your best to contain the situation by gathering the leaking water with a bucket or container of some sort.

We would recommend that you turn off the water stop tap as well as the heating itself, to prevent any further potential damage.

Have a check of your boiler pressure, and then finally, get in touch with a qualified engineer. We would strongly advise against attempting to fix the issue yourself. For peace of mind, leave it to the experts.

My Boiler Is Leaking Water From The Bottom

There is no sugar coating it. Leaking water from the bottom of your combi boiler isn’t good news. It Is usually to do with the piping inside your boiler corroding.

This isn’t uncommon, particularly in older appliances, but should be looked into as a matter of urgency. The science behind it is simple, it is what causes any metal to rust when exposed to water for long periods. The oxygen in the water mixes with the metal to create what is known as oxides.

As discussed earlier, if the problem is isolated to a smaller area of your boiler, there is a chance that it can be fixed. However, the larger the area of corrosion, the more likely you are to need a new boiler.

Is A Leaking Boiler An Emergency?

This depends on what you class as an emergency. There is no denying that a leaking gas tank is much more serious and dangerous than a leaking water boiler, given the immediate health and safety concerns that can arise.

However, if left unattended, leaking water from your boiler (1) (2) can cause irreversible damage to the appliance, and even parts of your home. We would strongly advise against leaving this problem to continue for too long. The more time left to leak, the more difficult it will likely be to repair.

Water Dripping From Boiler Pipe Outside

It isn’t beyond the realms of possibility that your boiler leaking water from the outside pipes is due to a fault at the installation phase. While this doesn’t automatically equate to a cowboy builder, the issue remains, and will need fixing.

Smaller water leaks, as you can imagine, are more difficult to spot. Not only that, they are quite common. Assuming that you opted for a reputable company to carry out the initial work, they should have no issue in returning to your property to fix the issue.

How To Fix A Leaking Boiler?

Let’s take a closer look at how you can employ that bit of DIY that we know our readers love. First and foremost, call an engineer, but in the meantime, take the below precautions.

Turn Off Water Supply

It’s simple really. Once you have located the problem area, the last thing you want is for it to continue. The first thing you should do is turn off your water supply. Your internal stop tap, usually located under your kitchen sink, is where you should head to here.

Turn Off Heating

Continuing to try and heat your home will likely see the problem continue, and possibly worsen. Turn off your central heating, and wait for the engineer to come and resolve the issue.

Drain Your Boiler

It is highly likely that there will be excess water gathered inside your boiler. Once you have turned off the stop tap and the heating, turn on a few taps around your house and flush the toilet. This will result in the excess water being drained, leaving a dry boiler for the repairman to work with.

Remove Excess Water

Speaking of the repairman, it will make their job much easier if they don’t have to contend with puddles of water when fixing your boiler. Take a look around the area and mop up any puddles that have gathered. After all, who wants puddles in their home?

Check For Insurance

Some, although not all, insurance policies cover water damage to boilers caused by fault piping. You are most certainly best to check this while you wait for the engineer to arrive. If you don’t have to pay for the repairs, that’s a needed bonus.

How Much To Replace A Damaged Boiler?

If your insurance doesn’t cover you for a broken water boiler, the next question you’re going to be wondering is “how much does it cost to replace a damaged boiler?”. In reality, this can vary from anywhere between £1,000 and £4,000. This price can alter based on labour costs, installation fees and the type of boiler that you opt for.

If you are working on a budget, you can purchase a conventional boiler from £500 and a combi alternative from £700.

At the other end of the scale, a high end alternative may cost anywhere between £2,500 and £4,000. As is the case in most walks of life, you pay for quality. So if you want to have confidence in your boiler, you may be best having a think about which price range best suits you and your needs.

How To Prevent A Boiler Leak?

Your best bet to prevent your boiler from leaking is to book it in for an annual service. Any minor problems can be fixed before they become a bigger issue that is more difficult to fix.

What’s more, an annual boiler service will also help to ensure that you aren’t overpaying on your bills through poor energy efficiency (read more: when can I switch energy supplier without penalty?).

A boiler service will usually set you back from £70 to £100. This cost will vary depending on the engineer in question, and where in the country you are based. Should you opt for boiler cover? Or a one-off boiler service? Each have their advantages and disadvantages, although boiler cover, at around £8-13 per month, means that you won’t have to shell out a lump some should you need major repairs or indeed a new system.

Take a read of our recent boiler service cost post before making your decision.

In conclusion, while leaking water from your boiler may not be as dangerous as a leaking gas tank, it still required urgent care. The best way to ascertain whether it is fixable, or whether you will require a new boiler altogether, is to speak with an expert. A fully-qualified engineer will be able to talk you through any potential repairs, as well as give advice on whether the time has come to replace your boiler.

You are most certainly best to acquire more than one quote for your repairs or replacement boiler. We wouldn’t advise going too low on your price, in the same way that paying over the odds for the sake of it doesn’t necessarily translate into quality workmanship.

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