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Why is My Boiler Leaking Water?

Bronte McClelland
By: Bronte McClelland
Updated: 17th June 2022

A boiler leaking water needs the urgent attention of a heating engineer as it could lead to serious damage.

Corroded pipes, high pressure and loose joints are all common causes of a boiler leaking water. If your boiler was only installed recently, the leak could be down to poor installation.

Should you spot even the slightest leak, contact a heating engineer right away. The water could lead to corrosion, rust or cause electrical parts to malfunction.

Is your boiler leaking water?

Boiler leaking water
If you’ve landed on this article, chances are your boiler is leaking. While you shouldn't attempt to repair the issue yourself, you can take a few steps to prevent more water leaking into your home:

  • Turn off the water supply
  • Switch off the heating
  • Wipe up any water
  • Contact a qualified engineer

Don’t attempt to repair the fault yourself – at the earliest sign of a leak you should ALWAYS contact a Gas Safe registered engineer.

Why is my boiler leaking water?

There are several reasons why water might be leaking from your boiler and the root cause can often be determined by where the water is coming from.


Corroded pipes or tanks could eventually begin to weaken, which may result in water escaping over time. Should the corrosion not have spread further than a single pipe or valve then simply replacing the corroded part will resolve the issue.

In the case that the corrosion has spread throughout the system, it's probably beyond repair and mean that you'll need to replace your boiler.


If your boiler pressure is too high then this could result in the boiler leaking water, this is because the boiler needs to let out some of the excess pressure to avoid the unit imploding.

You can tell if your boiler pressure is too high if the needle on the pressure gauge is pointing anywhere above 2. So if you can see that you boiler pressure is too high, you can simply reduce the pressure. The correct boiler pressure is between 1 and 2 on the pressure gauge.


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. Any leak from the temperature valve suggests that the boiler temperature is too high and could lead to scalding water coming out of the taps.

Pump seals

A boiler pump is there to pump water around your home's heating system. So, if it isn't sealed correctly, then the water can leak out. The pump will either need replacing or resealing.

Loose joints

Part of the natural wear and tear includes joints and pipe connections loosening over time as a result of the water repeatedly expanding on heating then and contracting on cooling. This means that the joints need to be tightened up to prevent water from coming out.

Poor installation

Finally, a leaking boiler could quite simply be caused by poor installation; this is often the case when water is coming from the pipe fittings.

To avoid this happening, you should only allow a Gas Safe registered engineer to install a new boiler. Use Boiler Guide to get free installation quotes from up to 3 fully-qualified heating engineers in your local area.

Wear and tear

Just like anything, 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.

This will not only be much less likely to leak but also increase the energy efficiency of your home, helping to save you money on your bills.

Is a leaking boiler an emergency?

A leaking boiler is a serious issue that can not only cause further damage to the boiler itself but also your home.

Ignoring a leak can lead to corrosion, rust and even mould. At the earliest sign of a leak (even if it seems relatively small) contact a heating engineer – don’t attempt to repair it yourself!

Can I use my boiler if it’s leaking?

If you spot a leak or find that the boiler pressure has dropped dramatically in a short space of time (suggesting a leak) then don’t use your boiler. Instead, switch off the water supply and the central heating and contact a Gas Safe registered engineer.

Does a leaking boiler cause low pressure?

A leak anywhere around your central heating system will lead to low boiler pressure. A boiler with low pressure won't be able to operate efficiently so getting the leak seen to by a professional is important.

How dangerous is a leaking boiler?

A leaking boiler has the potential to cause lots of damage, not just to the boiler itself but your home too. It's highly likely that water will be leaking onto electrical components that could end up short circuiting. Depending on where your boiler is and how far the water has spread, it could potentially cause damage to carpets, furniture and other belongings.

At this point, you may want to consider a replacement boiler.

How to prevent a boiler leakage

The best way to prevent your boiler leaking water is with an annual boiler service. This will ensure your system is running safely and bring any potential issues to the attention of a trained professional before they happen. It will also help to keep your boiler running safely, reliably and efficiently.

In addition, you could also have your heating system treated with a chemical flush. A flush of the heating system will remove limescale and debris that could help to reduce the risk of corrosion. A more longer term solution would be to have a magnetic filter fitted. A magnetic filter removes debris from the heating system before it has chance to build-up.

Why has my boiler has stopped leaking?

The most likely reason is that you've turned the central heating off, meaning that the pressure within the system drops and the leaking stops. One other reason could be if your area has recently experienced heavy rainfall as the water can get into the boiler via a poorly fitted flue. If this is the case, then you should contact an engineer who will be able to fit the flue properly.
Blaze: Best Gas Boilers

How to fix a leaking boiler

Don't attempt to stop the leak yourself, instead you should enlist the help of a qualified engineer.

You can do this really easily and quickly right here. By completing one of our simple online forms, you'll get free quotes from up to 3 trusted engineers in your local area. You'll then be able to compare the quotes and choose the best one for you, or not, as there's no obligation to use any of the quotes if they're not right for you.

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Bronte McClelland

About the author

Bronte McClelland

Brontë is one of our resident home heating experts. She has expertise in writing about renewable energy and heating systems, and continues to stay up to date with the latest trends and technology.

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