How to repressurise a Vaillant boiler

When you experience issues with your boiler, before jumping to the conclusion that it is a serious problem and you’ll need a costly engineer to fix it, it is often worth trying to repressurise your Vaillant boiler. Older Vaillant boilers in particular can sometimes just stop working and repressurising it is enough to get it working efficiently again. In this article we will be exploring what the pressure on your boiler should be and the steps involved in repressurising it back to within normal parameters. 

Checking Vaillant boiler pressure 

For many people it is often easier to not check the pressure on the boiler as it isn’t as simple as checking the gauge straight away. This is because Vaillant doesn’t include numbers on their manual pressure gauges, so for many homeowners it is hard to tell where the pressure actually sits. In order to get an exact number, you must press the buttons below the digital display and navigate to the right place. 

Like with pretty much all boilers, the normal pressure range should be at around 1.5 bar when the system is off and fully cold. However, you don’t need to worry about increasing the pressure unless it drops to below 1 bar. If the pressure increases to above 1.5 bar when the system is off, it is likely that your boiler pressure is too high and will need to be decreased. We’ll just be focusing on low boiler pressure for now though. 

How to repressurise a Vaillant boiler 

If you’re unsure about how to repressurise your specific boiler model, you will probably need to consult your manual. However, generally, by following the below steps you can get an understanding of what you need to do to increase the pressure of your boiler. 

1. Make sure the boiler has been turned off for long enough that the system is fully cooled. 

1. Find the boiler filling loop, it is normally located under the boiler. One end of the loop will have a handle valve and the other an isolation valve due it being the link between the main water supply and central heating. In some cases, the filling loop can leak which results in the pressure dropping. 

1. Check that the loop is securely fastened to prevent the risk of a leak and turn the isolation valve until it lines up with the pipe. 

1. Rotate the handle valve to allow the water to enter the system and monitor until the pressure levels get back to where they should be. 

1. Close both the valves securely to ensure no more water can pass through. 

1. Reset the boiler if needed and turn it on to check if the system is working. 

Some boilers won’t have a filling loop and instead use a key for repressurising the boiler. The steps for using a key rather than a filling loop remain fairly similar except the filling key is put into a keyhole and unlocked to allow the valve to be rotated and water to flow through. 

Your Vaillant boiler should not need to be repressurised often so if you notice the pressure dropping to below 1 bar consistently there is likely to be a deeper issue causing it. For example, a leak is a big cause of low pressure as water is escaping from somewhere. You will need to contact a Gas Sage engineer at this stage to locate and repair the leak before it has the chance to cause any further damage. 

Conclusion 

Knowing how to repressurise your Vaillant boiler is extremely important as it could help your boiler get back up and running efficiently without you having to call out a professional. Buying boiler parts new from manufacturers can quickly become expensive. As boiler spare parts suppliers, NBS provide high-quality refurbished boiler components at affordable prices. Find the parts you need for your boiler today and don’t hesitate to contact us if you have any questions.