Boiler leaking?


If you’ve got a leaking boiler you’ll understandably¬†be worried. For this article, I’m going to assume you’ve got a water leak and not a gas leak. If you’ve got a gas leak then follow the advice on this page. Boiler leaking issues can be pretty simple to diagnose, but, remember, you’ll need a Gas Safe registered engineer to help you fix the problem.

What to do if your boiler is leaking water

A leaking boiler can be caused by a number of issues and I’ll go through some of them for you now. This checklist should help you diagnose at least some of the most likely issues.

Try and find where the leak is coming from

If you know more about the leak you’ll be able to inform the engineer you call. You’ll save his time and hopefully, your money.

Where is the leak coming from exactly? Do you think it’s from pipework underneath the boiler? Or is it an internal boiler leak from a faulty valve or broken seal or corroded seal? Tak a look at the pipework below the boiler and see if it is wet. If some of the pipework has green in colour it indicates you’ve had a leak for quite a while.

If it’s a combination boiler then there will be 7 pipes in total and only one of them will be a plastic (usually white) pipe. If this has come loose then push it back into position – job done.

When is the leak occurring?

Check your boiler for leaks when it is standing still (i.e. not running) – is it leaking when it’s not being used? Now check if the leak is still there when the boiler is running (i.e. when the heating is on or the hot water tap is turned on).

Sometimes, when the heating or hot water tap is on and the boiler is running, the leak stops. This is because the hot water is making the pipework expand and ‘sealing’ the leak. You can confirm this by turning off the boiler and letting it cool and seeing if the leak starts again.

Is the boiler losing pressure?

If your boiler is leaking quite bad, you’ll notice a dramatic drop in the pressure gauge. You may notice some water is leaking outside from something called a pressure relief valve. If this keeps on leaking there is a fault because it should close off automatically once the system returns to an acceptable pressure. It could be stuck in the open position or it could need replacing – you’ll need an engineer to tell you which.

In some cases, the pressure relief valve will be working fine – it’s just letting excess water escape –¬† and instead, there could be a problem with the pressure vessel – that could need replacing as it isn’t doing its job properly.

Leaking boiler safety

A leaking boiler isn’t usually dangerous if it is a small amount of water or if it leaking outside from the pressure relief valve. However, as a non-qualified person, you should not risk removing the cover of the boiler or touching any other electrical equipment associated with the boiler.

A leak can get worse and cause more problem with the insides of the boiler – causing other parts to fail, corrode and rust. Your system will also contain a chemical that gets rid of sludge. If the system leaks, then it is losing this vital chemical and this needs to be looked at.

Leaking boiler advice

My advice would be to try and find out as much as you can about the leak to help identify what’s causing it and help answer any questions the engineer might have. Always use a professional gas engineer from the official Gas Safe Register.


About the author

Avatar for Ajvinder Singh
Ajvinder Singh

Ajvinder Singh holds a BA in Business and Management from the London School of Economics and Political Science. He is a regular contributor to Earth Easy, Green Prophet, and many other green living blogs. As well as holding fellow membership with the National Inspection Council for Electrical Installation Contracting and being on the Gas Safe Register, he is also a fully qualified Domestic Energy Assessor with Elmhurst Energy.

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