How to fix a boiler leak

When your boiler starts leaking, it’s important to get a Gas Safe registered engineer involved. If you have boiler cover, contact your provider straight away. They’ll be able to arrange for someone to visit your home and fix the problem. 

If it’s an external leak, there are a few things you can do while you wait for help: 

• Switch off the water supply – there’s a step by step guide on how to do this below 
• Turn off the central heating
• Contain leaks with cloths and containers 

Leaving the leak could cause rust or electrical damage to your boiler, so it’s important to act fast. 

How to switch off your water supply

Find the stop tap. This is usually under your kitchen sink. But it could be in an airing cupboard, under the stairs, or somewhere else in your home. If you can’t see it inside, remember it might be in an outbuilding.

Turn the stop tap off. Once you’ve found the stop tap, close it by turning the handle clockwise until it won’t turn it any further. Closing the tap will slow and eventually stop the water flow, helping keep your home safe from further water damage.

Let the excess water out. You might need to open the hot and cold water taps in your home slightly to drain the remaining water. This could take a few minutes, as there will be water in the pipes from before you turned the stop tap off. 

Can I use my boiler if it’s leaking?

You should switch off your boiler as soon as you notice a leak, before contacting a professional. Remember you might not always be able to see the leak, so look out for other signs like low water pressure and dripping noises. 

Why is my boiler leaking?

There are a few reasons why your boiler might be leaking. Remember, the best way to avoid a potential leak and disruption in your home is to get regular boiler checks and reliable cover.

Loose boiler joints

Every boiler will go through some natural wear and tear, which sometimes causes joints and pipe connections to become loose. If this happens, the joints will need to be tightened to prevent more water from leaking.

Broken pump seal

A boiler pump helps to push water around your heating system to keep your home warm. If it isn't sealed correctly, then it might start leaking. Older boilers are more likely to get leaks. But new boilers can get them too, especially if they’ve been running over pressure. An engineer can tell you whether your pump will need resealing or replacing.

Water pressure 

If your water pressure is too high, then you might be at risk of getting a leak. This is because the boiler needs to find a way to let out some pressure.

You can check if your boiler pressure is too high by looking at the pressure gauge. This should read between 1 and 1.5. If it’s above 2, then it’s too high and needs to come down. Here’s our guide on how to repressurise your boiler.

Tip: It’s also important to check your water pressure isn't too low. If it’s dropped below 1, it might be a sign there’s a leak somewhere in your boiler or central heating system that you can’t see. You’ll need to repressurise, and contact an engineer to repair the leak. 

Broken parts 

If your boiler is more than 10 years old, the leak might be caused by parts that are broken or worn away. An engineer will be able to check this for you. If your boiler shows signs of broken parts, it might be time to replace it.

Corrosion

Corroded pipes or a corroded water tank can sometimes cause a boiler leak. An engineer should be able to swap out specific parts. But if the corrosion’s spread further, then the whole boiler system might need replacing.

Poor installation

If your boiler’s fairly new, then your leak might be caused by poor installation. Look out for water that’s coming from the pipe fittings. Getting a Gas Safe registered engineer to install your system will make sure it’s done professionally.

Temperature

Boilers are fitted with a temperature control valve (TCV), which monitors the water temperature inside the boiler and stops it getting too hot. A leak that’s coming directly from the temperature valve could be caused by a high boiler temperature. If scalding water starts coming from your taps, you’ll need to contact a professional.

What should I do if my radiator is leaking?

A radiator leak can be caused by corroded pipes, a leaky valve, or loose pipe joints. If your radiator starts leaking, the first thing to do is put a towel below it and use a container to catch any water. This video from a qualified engineer will show you what to do.