How To Repressurise A Vaillant Boiler

How To Repressurise A Vaillant Boiler

Having a properly functioning boiler is essential for maintaining a comfortable and warm home. One common issue that homeowners may encounter is low boiler pressure. Luckily, repressurising a Vaillant boiler is a relatively straightforward task that you can easily do yourself without the need for professional assistance. In this article, we will provide you with simple step-by-step instructions on how to repressurise your Vaillant boiler and get it back to optimal performance.

Why Does Your Vaillant Boiler Lose Pressure?

Before we delve into the repressurising process, it’s important to understand why your Vaillant boiler loses pressure in the first place. The two most common reasons for a drop in boiler pressure are:

1. Bleeding radiators: If you have recently bled your radiators or carried out any maintenance work on them, the pressure in your boiler may have dropped as a result. This is because when you bleed radiators, air is released from the system, which results in a drop in pressure.

2. Water leaks: Another common cause of low boiler pressure is water leaking from the system. If you have noticed any visible signs of water leakage, such as damp patches or water stains near your boiler or on the pipework, it is important to address the issue of the leak before attempting to repressurise the boiler.

How To Repressurise Your Vaillant Boiler

Now that you understand the possible causes of low boiler pressure, let’s move on to the step-by-step process of repressurising your Vaillant boiler:

1. Find the filling loop: The filling loop is a flexible hose connecting the cold water main to your boiler. It is usually located below the boiler and consists of a valve on each end.

2. Ensure the boiler is turned off: Before you start the repressurising process, make sure the boiler is switched off and completely cooled down.

3. Close the valves: Locate the valves at each end of the filling loop and ensure they are both closed. You can do this by turning the handles clockwise until they are fully closed.

4. Open the valves: Slowly open both valves, turning the handles anti-clockwise, until they are fully open. This will allow water from the mains to flow into the boiler and increase the pressure.

5. Monitor the pressure gauge: Keep an eye on the pressure gauge on your boiler, and wait for the needle to reach the recommended pressure level. The ideal pressure for most Vaillant boilers is around 1.5 bar, but it’s important to consult your boiler’s manual or the manufacturer’s guidelines to find the specific pressure range.

6. Close the valves: Once the desired pressure is reached, close both valves by turning the handles clockwise. This will prevent any excess pressure from building up in the system.

7. Check for leaks: After repressurising your boiler, inspect the surrounding area for any signs of water leakage. If you notice any leaks, it is crucial to call a professional plumber to address the issue.

8. Restart the boiler: Finally, switch the boiler back on and ensure that it is running smoothly. You may need to reset the boiler following the repressurising process.


Maintaining the optimal pressure in your Vaillant boiler is essential for its efficient and reliable operation. Repressurising your boiler is a relatively simple task that you can do yourself, provided you follow the correct steps. By following our step-by-step guide, you can repressurise your Vaillant boiler and ensure the comfort and warmth of your home throughout the year. However, if you encounter any difficulties or are unsure about any aspect of the process, it is always best to seek assistance from a professional heating engineer.

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