Boiler Leaking Water?

Learn about how to diagnose a leaking boiler and when to call in a professional to fix the problem.

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A boiler leaking water is usually a sign that a seal or a valve has developed a fault. However, if the problem is left untreated, a leaking boiler can cause other components to erode as well as cause damage to the electrical components within the boiler. Your best option when you notice a leak is to fix the problem quickly to prevent further damage.

Below, you can find out how to determine why your boiler is leaking water.

Please note that this article is provided for information purposes only - for any repairs, or if you need to take the cover off for any reason, you will need to contact a qualified mechanical contractor to perform the work.

Why is my boiler leaking water?

Before you can do anything with  your boiler, you need to find out why it’s leaking, but this isn’t always easy. The first thing to do is find where the water is coming from, as this will give you a better idea of why. Below, we’ve listed some of the main causes of a leaking boiler.

High boiler pressure

Have you ever noticed the gauge on the front of your boiler? This is important as it tells you how much water pressure there is in the system. Too little or too much pressure can cause a problem, so you should check the valve regularly and add or remove water as required.

If your boiler is leaking, you should check the pressure gauge to see if the pressure is too high. If this is the case, it’s likely that the pressure relief valve is trying to release some of the water in the system to bring the pressure back down to a comfortable level, which can lead to your boiler dripping water. The valve needle should be between 1 and 1.5 bar (usually shown on the gauge as a green zone). If the needle is higher than this, or in the red zone, you may need to bleed the radiators to release extra water.  

Corrosion in your system

Corrosion can be a problem in older boiler systems as it can cause rust and other debris to build up within your radiators and pipework. As the water runs around the system, it can pick up this debris and return it to your boiler. The older the system, the more likely you are to have issues with corrosion, which in turn can lead to your boiler leaking water from the bottom. Unfortunately, many people don’t know corrosion is there as it can’t be seen.

Corrosion can break the rubber seals around the joints of pipes, so water may be leaking through here. If the corrosion is on an individual component, an experienced contractor will be able to replace this with ease. However, if the corrosion is widespread, then you may need to  replace the boiler completely.

A contractor will be able to advise you if a new system is required or if a new boiler and a flush of the system would be adequate. If you have an old boiler, replacing it with a newer model could make your home more efficient and could save money on your gas bills, too.

Faulty heat exchanger

The heat exchanger is the piece that allows your boiler to heat cold water, so it’s a very important part of the appliance. Unfortunately, a leaking boiler can be a sign that the heat exchanger is starting to decay. It’s not uncommon for this part to crack in some models over time, and it can be expensive to replace.

This isn’t a problem that you’ll be able to diagnose yourself, as it involves taking off the cover of the boiler and looking inside. Therefore, you should call a licensed contractor to check the issue for you. Some boilers are more susceptible to corrosion due to the materials they are made from. Viessmann heat exchangers offer a 10-year warranty.

Is a leaking boiler dangerous?

While a boiler leaking water may not present an immediate danger, it should be checked to ensure that the problem is solved quickly. This avoids the issue becoming worse or leading to more dangerous issues.  

How to fix a boiler leaking water

Now that you know why your boiler might be leaking, you need to know how to fix the issue and stop that boiler leak.

As we’ve mentioned, first you should check the pressure gauge. If the pressure is too high, bleeding some of your radiators to release a bit of water should help with the issue.

Next, you should see if the water is coming from any visible pipe fittings or joints. To check, dab the area dry then wait to see if the water appears again. If it does, you can try turning the connector by just a quarter turn using a spanner to see if this stops the boiler from leaking water. It may be that a seal has come loose and just needs to be tightened.

However, corrosion can cause some seals to wear away, allowing water to escape. If this is the issue, you’ll need to get a suitably qualified heating contractor out to take a look at the seals and  replace them where necessary.

If you cannot determine the issue yourself, or need someone else to delve a little bit deeper into the problem, you should call a professional. There are many excellent contractors who will give impartial advice as to the most cost-effective solution to fixing your leaking boiler.

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