How to repressurise your boiler

As winter arrives no one wants a problem with their central heating, and yet a simple issue could shut down your system in an instant.

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Most condensing boilers and many standard boilers are installed as pressurised systems. This replaces the older systems which relied on a water tank, normally situated in the highest point of the property with a float device to top up water levels. In the absence of the self-filling option, a pressurised system will need manual filling via a loop installed on your boiler. Do not be concerned as this is a simple operation known as repressuring and involves injecting water into the system via the cold water supply.


The problem is often caused by what can be a small leak in your piping system which may not be a serious problem, but it will mean your boiler will need to be repressurised.

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When you find the system is not working check your boiler. There will probably be warning lights flashing and you should check your documentation and instruction manual to ensure that this is a pressure problem. Another clue will be that the pressure gauge will show a reading of less than 1 and 1.5 bars. Try to keep an eye on this reading once a month, and if the pressure has fallen, give it a boost in the manner described below.

Filling loop

However, if the problem is not indicated by either the warning lights or pressure gauge you may need professional help. Advice on this can be found at the government Health and Safety website.

Wherever you have had a boiler installation Gloucester, Exeter or Aberdeen expert advice will be available at sites such as

If you have established that the issue is a fall in pressure, then you need to locate the filling loop. This should be easily identifiable as the input will be via a metal hose attached to the boiler with a stop tap. Use this tap to introduce water into the system and you will see the pressure gauge begin to rise. Close the tap when you have reached the safe pressure.

Your boiler installer or your maintenance engineer will be happy to talk you through repressurising, which is a simple process once you understand it, so don’t let a simple fall in pressure on your system cause you problems.

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