Why Is My Boiler Leaking? (How to Fix a Leaking Boiler)

If you have noticed a leak coming from your boiler, it is important to work out the cause and get it fixed quickly to avoid any further damage being done to your home and heating system. 

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In this guide, we will be looking at some of the most common causes behind a leaking boiler and what you should do if you have found a leak.

Common Causes of a Leaking Boiler

There are several reasons why water may be leaking from your boiler, and the root cause can usually be determined by identifying where the water is coming from. 

Below is a list of the most common places where a leak can come from:

Corroded Components

In most cases, the pipes immediately beneath the boiler are to blame for a boiler leak.

This is because, over time, pipes and other components inside your boiler can start to corrode, creating small holes that water can escape from, resulting in a boiler leak. 

If just one part of the heating system has become corroded, then you will only need to have that part replaced to solve the issue.

However, if multiple parts inside the boiler have corroded, it will likely be beyond repair, and you will require a new boiler.

If your boiler is new and has recently 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. Still, if this is the case, the installation 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 you must use a reputable boiler company with qualified Gas Safe Registered engineers for all services.

High Boiler Pressure

If your boiler pressure is too high, you may find that water starts to leak from it as the boiler attempts to release some of the excess pressure to avoid imploding.

An easy way to tell if your boiler pressure is too high is by reading the gauge.

If the needle points anywhere above 2, your pressure is likely too high and must be lowered to between 1 and 2 (or the green section).

To do this, you should first try bleeding your radiators to release some of the pressure.

If this doesn’t fix the issue, please refer to your manufacturer’s guide and follow the instructions on what to do.

Faulty Heat Exchanger

Sometimes, in lower-quality boiler models, the heat exchanger can fail, crack or become damaged.

Without a qualified Gas Safe Engineer, it can be incredibly difficult to tell if the issue is due to a faulty heat exchanger, however, if this is behind the boiler leak then you would be looking at a very hefty repair bill due to the high cost of the replacement part. 

That’s why we would recommend getting a higher quality boiler replacement instead, as this will be greater value for money and less likely to break down in the future.

Loose Joints

Over time, parts of your heating system will see some wear and tear.

This can sometimes mean your joints and pipe connections become loose due to the water repeatedly expanding on heating and then contracting on cooling. 

To fix the leak, try tightening the joints and pipe connections.

High Temperature

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

If you notice your boiler leaking water from the temperature valve, the boiler temperature is likely too high and could result in scalding water coming out of your taps.

To lower the temperature of the water from your boiler, locate the adjustment needle on the thermostatic expansion valve.

Turn the adjustment needle one 45º anticlockwise to decrease the temperature. Each 45º turn is equal to one degree. 

Pump Seals

The boiler pump is designed to push water around your heating system; however, if the pump isn’t sealed correctly, water can escape causing a leak.

If you notice water coming from your boiler pump, you will likely need to reseal it or replace it.

Overflow Pipe Leaking

An overflow pipe leads from a water storage tank or cistern inside your home to the outside. 

When an overflow pipe is dripping or running with water, one of the most common causes is a problem with a float valve.

Float valves are found in toilet cisterns, cold water tanks, central heating feed, and expansion tanks. 

It’s the component that controls the water level and consists of a metal or plastic arm with a plastic ball on the end that floats on the water.

If the float valve is damaged or there’s a puncture in the plastic ball, it must be. 

To do this, shut the water supply off and drain the cistern. 

Remove the float valve and purchase a new one from your local DIY store. Then, reinstall it.

Help! My Boiler is Still Leaking!

If you still cannot find the cause of the leak in your boiler, your best bet is to turn off your water and get in touch with a local Gas Safe Engineer immediately before any more damage can be done to your property.

The engineer should then be able to identify the cause and recommend either a fix or a new boiler.

If this is the case, you can make replacing your boiler much quicker and easier with iHeat.

Get a free, fixed quote on a brand new A-rated boiler today!

For more information and advice, check out the rest of our handy boiler guides in our blog.

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