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Boiler Leaking What Should I Do?


Picture this; you go to sleep only to wake up to a flooded kitchen. You look for the source of the leak and discover it’s the boiler. From experience, you know leaks are bad news. But how do you fix the problem? Can you handle it as a DIY or should a Gas Safe engineer fix the problem instead?

You should note that there are several reasons why your boiler could be leaking. In this piece, we shall look at a couple of these causes.

Determining why your boiler is leaking

Before anything else, we should stress the importance of acting fast. A leaking boiler isn’t something to ignore. It often implies there’s a severe problem with your system, including a broken valve or seal.

A leak could cause other components to rust or even worse, short circuit the electrical system in the boiler. It is difficult to diagnose the cause of the leak in the boiler. But before calling in an expert Gas Safe engineer, you should inspect the below cases.

Why your boiler is leaking water and how to fix it?

Boiler pressure too high

Boilers and pressures are often mentioned in the same sentence – and for a good reason. Boilers need to operate at a specified optimum temperature. High boiler pressures can result in faults and breakdowns.

Also, the boiler might start gurgling, and clanging and the pressure release valve might start leaking. The leak can cause some internal components to fail.

Checking for boiler pressure

Modern boilers have pressure gauges on their front panel (they look like speedometers). For System and Combi boilers, the pressure gauge should read 1 bar and fall within the green bar. Anything above the green bar means the pressure is high.

Fixing high boiler pressure

Reducing boiler pressure can be achieved by bleeding the boiler system. The process is simple. But before you proceed to drain the boiler, confirm the filling loop tap under the boiler is closed. This is essential especially if you topped up the boiler pressure in the recent past. If you can’t tell if the tap is closed, turn it and if the pressure starts to rise, close it.

The next step is bleeding the system. The process is simple and doesn’t require any special expertise. However, you’ll need a bleed key to loosen the nut on the radiator. Turn it and let air and water flow out into a bucket below.

If the boiler continues to leak after this, consider buying a new boiler.

Corrosion and general system wear

When ignored for a while, corrosion leads to leaks. Extensive corrosion means you’ll be getting a new boiler in the near future. But before taking this step, have the boiler inspected by an engineer as it could be saved.

Once you get a quotation for a repair, weigh the cost of repair against that of buying a new boiler.

Checking for corrosion

The process is all about visually looking out for rot in the boiler system. Inspect hidden spots that are in contact with water.

How you can fix the corrosion

Unfortunately, there is little you can do to cushion your bank account from the strain. Whether it is a repair or a new boiler repair, you should have a Gas Safe engineer handle it.

Leaks from seals on internal parts

You can think of boilers like humans. They have fluids flowing through their system. The fluids flow in specified channels. In case of a change of course or internal bleed, the repair needs to be immediate.

Many internal bleeds happen on the joints and seals of internal components. These parts give in to the boiler pressure or decay over time. When a seal fails, water gushes out at a surprising rate.

Checking for leaks on the seals

If you are comfortable looking around under the hood of your boiler, you can inspect the boiler seals. However, you shouldn’t touch anything you don’t know what it is.

Fixing leaks on the seals

You should always leave this to professional heating engineers to handle the leak. A small sealing issue can be fixed quickly and cheaply. However, a bigger seal leak problem caused by corrosion might result in buying a new boiler.

Faulty heat exchanger

Boiler heat exchangers are the most expensive boiler components. Luckily, they don’t often crack or fail in boilers except for low-quality boilers.

How to check for a leak in the heat exchanger

To identify the leak, you need to get in touch with a Gas Safe engineer to help with the diagnosis. If the diagnosis is a cracked or faulty heat exchanger, it means your boiler is terminal. The repair might cost you a lot of money.

Fixing a faulty heat exchanger

Heat exchangers can be replaced. However, the process should be handled by a Gas Safe engineer. Since the replacement cost is steep, you are better off replacing the whole boiler instead.

Before you get a new boiler, consult a Gas Safe engineer to determine the perfect boiler size for your home.

Is a leaking boiler an emergency?

A leaking boiler is not dangerous. So in that sense, it is not an emergency. However, this doesn’t mean that you should ignore it. If you wait for too long, a leak that could be fixed escalates into a huge problem that costs a lot of money to fix.

Also, depending on where the boiler is located and where the leak is, the boiler could cause damage to furniture, carpets and other valuables in the house.

Is this issue common in Vaillant, Worcester, Baxi and Ideal boilers?

Yes, boiler leaks are common in all the named boiler brands. Each of the boiler brands has error codes that point to possible leaks in the system. Below are the error codes to look out for.

Worcester Bosch

Leaking error codes: HO7, CE207, E9, A1. These codes apply to Worcester CDI Class, Worcester Greenstar 25i, Worcester CDi Compact, Worcester Greenstar 30i and Worcester CDi Highflow.


Leaking boiler error codes: S.53, S.41, F.73, F.13, F.24, F.22. These error codes apply to Vaillant EcoTEC Pro, Vaillant EcoTEC Plus and Vaillant EcoMax Pro.


The error codes include: 118, 117, 125, H.02-06, E78.


The error codes include FD, L1, F1. They apply to Ideal Logic Plus, Ideal Logic, Ideal Mini, Ideal Independent, Ideal Isar, Ideal Vogue.

Preventing a boiler leak

Conducting an annual boiler servicing through a Gas Safe engineer will make sure the system runs smoothly without potential issues. Regular servicing will catch problems before they escalate into big problems that are difficult to fix.


Though there’s no need to wake up everyone in the house when you notice a leak, you still need to conduct a thorough diagnosis and fix it as soon as possible. If the leak is small, it’s probably because of a loose boiler seal. This can be repaired quickly and easily. But most importantly, the repair will be cheap.

However, if the leak is more prominent and your boiler is off, then the repair might be costly. So instead of investing your money in repairs, you should get a new boiler. A new boiler will benefit you with energy efficiency and save you money. In the long run, the new boiler might buy itself through the energy costs it saves you over two years.

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