Leaking boiler? Here’s what to do  

First things first: Let's stop your boiler leaking

If your boiler is leaking, do this right away: 

• Turn off the water supply at your stopcock– this will stop the leak from getting worse.  

• Turn off the mains electricity to your boiler to avoid electrical issues. 

• Contain the leak with a bucket and mop 

• Call a Gas Safe Registered engineer to take a proper look. 

Most boiler leaks will need a Gas Safe Registered engineer

Now that you’ve stopped the leak, let's find out what to do next.  

While some boiler leaks can be sorted easily (we’ll point these out below), most fixes involve repairs to the boiler and pipework, so should only be done by a Gas Safe Registered engineer.  

Good news – we know a few. Our heating engineers are on hand to get the job done. 

Why is my boiler leaking?

Leaks can come from a few places, and where the water is dripping from can give you a clue about what’s wrong. Let’s start with the easy fixes first: 

Blocked or frozen condensate pipe

This pipe connects to the boiler and leads outside, where it lets out any wastewater that builds up when your boiler does its thing. If it’s blocked or frozen, water backs up which can lead to leaks in the pipework. 

What to do: 

If it’s frozen and easy to reach, placing a hot water bottle on the frozen section will thaw the blockage and stop the leak.  

If it’s blocked or inaccessible, just Ding it.   

Boiler pressure is too high or there’s a faulty pressure relief valve

If your boiler has a pressure gauge, chances are it will have a pressure relief valve (PRV). 

The PRV keeps your boiler safe by letting out excess water when your boiler pressure is too high. If you’ve never seen this before, it might look like a leak but it’s actually a safety feature.  

However, if the PRV is worn or faulty, it might leak even when pressure is normal. 

What to do: 

If your boiler pressure is above 2.5 bars on the pressure gauge, bleeding your radiators until the water comes out can help reduce the pressure. If this doesn’t help, book an engineer for a repair. 

Leaking boiler causes – when to call a heating engineer

Boiler dripping water from the bottom

Corroded pipes

If your boiler is leaking from the bottom of the unit itself, then the pipes inside your boiler could be corroded. This is more common in older boilers.  

What to do:

Book a Gas Safe engineer to inspect the boiler. If just one pipe is damaged, they might be able to replace it. If corrosion has spread, it could be time for a new boiler.  

Whatever the outcome, your engineer will be able to open the boiler and let you know what’s going on. 

Faulty heat exchanger

The heat exchanger plays a big role in heating up the water in your home. If it cracks, it can start to leak – if it does, you'll usually see water coming out of the bottom of the boiler casing. 

What to do: 

This is a job for a Gas Safe engineer. The heat exchanger might need replacing. 

Leaks from the pipes leading to and from the boiler

Installation problems

If you've had a new boiler installed and it’s started leaking, it’s probably not an issue with the boiler. Instead, it’s likely the installer made a mistake during the installation.  

What to do: 

Call your installer to come back and fix the problem. You should be completely satisfied that your new boiler works and has been installed in the right way.  

Loose joints or damaged seals

General wear and tear can take a toll on pipe joints and seals.  

What to do: 

This is a common problem and fairly simple for a heating engineer. A quick tighten of the loose joint or seal replacement by a pro usually does the trick. 

Can I use my boiler if it’s leaking?

Nope. Switch it off, shut off the water, and book a Gas Safe engineer. Better safe than soggy. 

Need help with your leaking boiler? Just Ding it

Boiler leaks aren’t DIY territory, so get the experts in. With Ding, you get fast access to trusted Gas Safe engineers—no hassle, no fuss. Clear pricing, quick booking, and expert repairs.

Try Ding today. Your boiler’s new best friend.

Written by:

Martin Garbutt

Head of Technical

Martin has more than 30 years' experience in the gas industry working in all sorts of roles; from gas regulators to the private sector.

At Ding, he makes sure the technical information we share in the field and online is up-to-date and accurate. That includes helping to write helpful articles like this one.

View Martin's profile