My boiler is leaking – what do I do?

Leaking boiler pipe

If your gas boiler is leaking, you should never attempt to repair it yourself, as working with gas can be very dangerous. Gas boiler repairs should always be conducted by Gas Safe Registered engineers.

The below guide is for information only, and we do not recommend that you try to repair your boiler yourself. As soon as you notice a boiler leak, you should shut off the gas and water supplies to your boiler and contact a Gas Safe Registered engineer.

Why is my boiler leaking?

Determining the cause of a leak can be very difficult without taking the unit apart, which is why it is recommended that only a Gas Safe engineer deals with the diagnosis and repair. The below is to give you an idea of the potential causes of boiler leaks and to help you to prevent them from happening in the first place.


Corroded pipe

Corrosion is the most common cause of boiler leaks. If your pipes are corroded then this will allow water to escape, which often results in a loss of pressure and inefficient running. If the corrosion is isolated to a single valve or pipe, you may be able to simply get this one component replaced.

If the corrosion is more widespread, however, then it may be necessary to replace the entire boiler. This is often both cheaper and safer than trying to patch up a lot of smaller problems.

Pressure valve

Boiler pressure gauge

A leak from the pressure valve is usually a sign that the boiler’s pressure is too high. A boiler’s pressure should be around 1 bar (or 18-21 PSI). When this pressure is exceeded, water leaks from the pressure release valve to let out some of the excess pressure and prevent the boiler from rupturing.

A build-up of limescale or other debris can cause boiler pressure to increase, which can lead to it reaching unsafe pressure levels. The debris must be removed and the valves resealed in order to maintain the safety of the pressure release system.

Temperature valve

If you notice a leak coming from the temperature valve, this could mean that the boiler’s temperature is too high. This is often due to a fault with the temperature sensors within the boiler, which will need to be replaced to prevent scalding water from being sent out of the taps and causing serious injury.

Pipe fittings

If the leaks are coming from the pipe fittings then this could be a sign of an incorrectly fitted boiler. A Gas Safe Registered engineer may be able to bring the boiler up to code, but this is not always possible. Depending on how poorly the installation was carried out, you may find that the whole boiler needs replacing.

Pump seals

Leaks from the seals of the boiler pump will mean that the pump will either need to be replaced or resealed.

Other causes

There are many other causes of boiler leaks which are not listed here, and identifying the precise reason for your problem is not always straightforward. This, along with the potential danger of working with a gas appliance, is why you must always seek the services of a Gas Safe Registered engineer if you experience a boiler leak, and make sure that your boiler undergoes regular servicing to catch issues early before they develop into something more serious.



VHL’s Gas Safe Registered engineers are on hand 24/7 to repair your boiler should you notice a leak. Contact us today to benefit from over 20 years of boiler expertise.

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