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Leaking boiler?

If you’ve just discovered a puddle of water beneath your boiler, you need to act quickly. Ignoring a leak could lead to serious damage, so you should contact a Gas Safe engineer without delay. But whilst a leaking boiler isn’t a good sign, it doesn’t necessarily mean the end of the road for your boiler. Your leak could be due to something as simple as a faulty seal. In this guide, we look at some of the possible causes of your leaking boiler, and discuss possible fixes, so that you have a better idea about your boiler’s prognosis!

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Why is my boiler leaking?

If you’ve just discovered a puddle of water beneath your boiler, you need to act quickly. Ignoring a leak could lead to serious damage, so you should contact a Gas Safe engineer without delay.

But whilst a leaking boiler isn’t a good sign; it doesn’t necessarily mean the end of the road for your boiler. Your leak could be due to something as simple as a faulty seal.

In this guide, we look at some of the possible causes of your leaking boiler. And discuss possible fixes, so that you have a better idea about your boiler’s prognosis!

What are the signs of a leaking boiler?

Whilst this sounds like a daft question; there are actually a few signs that your boiler is leaking, aside from the obvious puddles of water!

Your boiler might also have a leak that you can’t see. Other clues that your boiler has a leak are a slower than usual heating process, and low water pressure.

Low water pressure is easy to identify on combi and system boilers that have a pressure gauge. The pressure in your boiler should generally be between 1 and 1.5 bar.

If your gauge shows pressure below this; or dropping pressure; it could indicate that you have a leak in your system.

Is a leaking boiler dangerous?

Whilst a leaking boiler is alarming and inconvenient, it isn’t usually dangerous.

But, that certainly doesn’t mean you should ignore the problem!

Even a slight leak has the potential to do irreparable damage to your boiler, as well as damaging your home.

So, you should get your boiler looked at by a heating engineer as soon as possible.

The quicker you act, the more likely you are to be able to minimise the damage to your boiler; and avoid the need for a full boiler replacement.

Can I use my boiler if it’s leaking?

If your boiler is leaking, or it’s pressure has suddenly dropped (suggesting a leak) then you shouldn’t use your boiler. Instead, you should follow the steps below.

My boiler is leaking, what should I do?

If you’ve spotted a leak, you should follow these simple steps to minimize any further water damage:

  1. Turn off your water supply

To prevent a puddle from growing, it’s a good idea to stop the water supply to your boiler. To do this, you can turn off your stop tap, which is often located under your kitchen sink.

  1. Switch off the heating

Next, you should switch off your central heating.

  1. Clear up or collect any water

Try to find where the leak is coming from; and use a container to collect any dripping water that might damage your floor. Wipe up any water that’s already been spilled.

  1. Contact a qualified engineer

Don’t attempt a DIY job on your boiler! Only Gas Safe registered engineers are able to work on gas appliances, so you should contact your engineer to take care of the problem.

Why is my boiler leaking water?

Now that you’ve contained the leak, you might be wondering what the possible cause is. And how expensive a repair is likely to be!

There are lots of possible causes of a leaking boiler; and the location of the leak often provides a clue as to what the problem is.

Here are some of the most common causes:

Possible cause of a leaking boiler: High pressure

Whilst low pressure is a possible sign of a leaking boiler; too much boiler pressure can be a cause of the leak.

High boiler pressure is one of the most common causes of a leaking boiler.

Modern boilers require constant water pressure to function properly. If the level of pressure rises too high; the boiler’s pressure release valve (PRV) will automatically release some of the water in the system to bring the pressure back down.

Excess pressure can also cause boiler parts to malfunction which can also create a leak.

It’s easy to check your boiler’s pressure, by looking at it’s pressure gauge. This is usually located on the front of your boiler.

If you have a digital gauge, it will often flash if there’s high pressure. It might also be showing a fault code.

If you have a hydraulic pressure gauge; the valve needle should be in the green zone between 1 and 1.5 bar.

If the needle is higher than this; or in the red zone; the pressure in your system is too high. And this is a likely cause of your leak – i.e. the PRV discharging the excess water, or internal parts failing under the pressure.

Whilst it’s possible to reduce boiler pressure yourself by bleeding your radiators; if you have a leak it’s better to get an engineer to take a look.

Possible cause of a leaking boiler: Corroded pipes

If you’ve noticed dripping water coming from underneath your boiler, corroded pipes could well be the culprit.

Over time, your pipes can break down, or ‘corrode’, causing small gaps where water can leak out from.

Corrosion happens as a result of your metal pipes reacting with the water; oxygen; dirt and debris within your heating system.

If the corrosion is limited to a single area; you may be able to replace the corroded part and resolve the issue. But if the corrosion is more widespread, it’s possible that a boiler replacement is on the cards.

While you wait for an engineer to look at your boiler; you should place a container bowl or underneath your boiler to catch any drips.

If you can see where the leak is coming from; you could also tie a cloth around the pipe to temporarily reduce the dripping.

Possible cause of a leaking boiler: Loose joints

If water seems to be dripping from the joints on your pipes, and the pipes themselves don’t look corroded; it could be that the joints have loosened and just need tightening up.

It’s possible for pipe connections or joints to loosen over time; due to the constant expanding and contracting of water during the heating process.

Possible cause of a leaking boiler: Poor installation

Another possible explanation of water dripping from pipe fittings is poor installation.

If your newly installed boiler is leaking water from the bottom; and there doesn’t appear to be another possible cause; it might be that pipe fittings and joints have not been fitted or tightened correctly.

To avoid this problem, you should only allow a Gas Safe registered engineer to work on your boiler.

Possible cause of a leaking boiler: Pump seal problems

A boiler pump’s job is to pump water around your home’s heating system. And as you can imagine, it’s put under constant pressure.

Over time, the seal on the pump can deteriorate or split; causing water to leak out; often at an alarming rate!

It may be possible to replace or reseal your pump. But if the damage is too great; and you have an older boiler, a boiler replacement might be the best option.

Possible cause of a leaking boiler: Temperature problems

Boilers are fitted with a temperature control valve (TCV) which monitors the temperature of the water within the boiler; and stops it from getting too high.

So, a leak from the TCV suggests that the boiler temperature is too high. And could lead to scalding water coming out of the taps. Obviously you need to deal with this as soon as possible to avoid possible injury.

Possible cause of a leaking boiler: Faulty heat exchanger

If your boiler is in its golden years; a leak from the bottom of the appliance could be caused by a corroded heat exchanger.

The heat exchanger is the part of your boiler which heats the cold water for your radiators and taps; so it’s a vital part of your boiler.

Unfortunately, a faulty heat exchanger usually means curtains for your boiler, because it’s the most expensive part to replace. If your boiler is old and out of warranty; it will probably make more sense to invest in a new boiler.

If you want to avoid future problems with your heat exchanger, we recommend ATAG boilers.

All ATAG boilers feature a revolutionary iCon heat exchanger, which has unrivalled performance and efficiency levels. It’s made from high grade stainless steel and, uniquely; it maintains 98% of its original efficiency levels throughout its lifetime. And best of all? It comes with a lifetime guarantee!

Possible cause of a leaking boiler: Wear and tear

Unfortunately, boilers don’t last forever and can wear out with time. If your boiler is older than 10 years, it’s probably time to consider installing a new one.

With a new boiler, you’ll benefit from increased comfort; energy efficiency; and will get a new guarantee. This gives you the peace of mind that should anything go wrong with your boiler in the future; it’ll be covered.

The Heating People can offer guarantees of up to 14 years on our boilers.

How to prevent your boiler from leaking

A leaking boiler is worrying, inconvenient and potentially costly. So, you’ll want to prevent it from happening again in the future. Here are some tips on avoiding a leaking boiler:

Prevent a leaking boiler: Get Repairs Done Quickly

Even if the leak is only slight, it’s important to deal with it quickly. A leak of any size is telling you that there’s a problem, and left untreated, it will only get worse.

What starts as a loose joint can become a much bigger (and more expensive) problem; because the escaping water will potentially damage other parts of your boiler.

To avoid a hefty repair bill; or the need to replace your boiler entirely; you should contact an engineer without delay.

Prevent a leaking boiler: Get your boiler serviced every year

As with anything, prevention is better than cure. The best way to prevent your boiler from springing a leak, is to maintain it with an annual service.

Boilers are the hardest working appliance in your home, and will wear down over time. They need regular maintenance and upkeep to enable them to run safely and smoothly for as long as possible.

Regular boiler servicing ensures that your boiler is running safely and any problems can be spotted and fixed early.

Failing to keep up with servicing will invalidate your boiler’s guarantee; which means that the cost of repairs won’t be covered.

Prevent a leaking boiler: Consider a Power flush

Before and after a power flush.You could also ask your engineer for advice on whether your heating system would benefit from a power flush.

A Power flush is a cleansing process that removes dirt and debris from your heating system. This could help to reduce the risk of corrosion.


To summarise then…

Whatever the size and probable cause of the leak; you should always contact a Gas Safe engineer to investigate as soon as possible.

Ignoring a leak could damage the electrical components within your boiler, not to mention the potential damage to your home.

Whilst some leaks have an easy and cheap fix; other leaks might indicate the end of the road for your old boiler that has been heavily corroded and worn down over time.

If you’re trying to decide whether it’s time to replace your boiler; contact one of our friendly team to book your free survey.

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