How To Repressurise A Boiler

Learn how to repressurise your boiler yourself in a matter of minutes with our tutorial guide.
Written By: Richard Morgan | Updated:
How To Repressurise A Boiler
Richard Morgan/DIY Works

If your boiler loses its pressure, you may need to repressurise it in order to regain hot water.

Luckily, unlike other problems with your boiler, repressurising doesn’t require an engineer callout as it’s something that you can do yourself, and below we explain exactly how to do it.

How To Check Boiler Pressure

Whether you own a Baxi, Glow Worm, Potterton, Vaillant, Worcester or any other combi boiler, they will all have a pressure gauge. The gauge’s location is usually on the front panel, and when checking your boiler’s pressure, you’ll want to check it whilst it is off and cool.

What Pressure Should It Be?

Most boiler brands in the UK recommend that the pressure of your combi boiler should be between 1 and 1.5 bar.

If the pressure is below 1 bar, you may have lost some water from a leak. However, if the system reads higher than 2 to 2.5 bar, you must release some pressure by bleeding the radiators.

To make repressuring your boiler even easier, most gauges will have a “green” zone that indicates the required pressure, and you should aim to be within this zone for the most efficient boiler pressure.

How To Repressurise A Boiler

  1. Switch off your boiler and allow it to cool down beforehand.
  2. Locate the filling loop (as shown in the below photo).
  3. Check for any leaks in the loop or around the boiler.
  4. Open both valves to allow cold water to enter (you should hear it enter the boiler).
  5. Leave the valves open until the pressure gauge reaches 1.5 bar
  6. Close both of the valves once the pressure has been achieved.
  7. Turn on the boiler and reset it if required.
how to repressurise a combi boiler

Richard Morgan/DIY Works

How Long Does It Take?

The time it takes to repressurise a boiler highly depends on how much water has leaked out. However, it shouldn’t take any longer than 10 to 20 seconds, but if it does, this may signify that you have a leak.

How Often Does It Need To Be Done?

The process of repressurising a boiler isn’t a common task that you are expected to carry out. If you are repressurising a boiler on a regular basis, this is a sign that there is a problem, and you should call out an engineer. The most common problem is that there is a leak in the system, which will need further investigation.

Other Factors To Consider

Although most households in the UK use combi boilers, there are some exclusions regarding repressurising a boiler. For example, if you have a conventional boiler system, you shouldn’t ever have to re-pressurise it because it uses a self-filling water tank that controls your pressure.


Once you have repressurised a boiler, you will find it much easier the next time because it is a very easy and straightforward task you can do yourself.

However, if you still don’t feel confident after reading our guide to repressurise a boiler above, we would recommend reading your boiler brand’s user guide. Most people will overthink it, but it really is very easy to repressurise a boiler and something you should try out before calling an engineer.

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