Vaillant Pressure Reliefe Valve

F20 Vaillant Fault Code - What Does The Vaillant F20 Error Mean?A faulty Vaillant pressure relief valve (PRV) doesn't typically trigger a specific fault code but will cause a continuous pressure drop, leading to an F22 error code (low water pressure) on the boiler display. You can identify a faulty PRV by signs like water dripping from the external overflow pipe or the boiler frequently needing to be repressurised. If the F22 code persists after repressurising the system to the recommended 1.0-1.5 bar, it strongly suggests a problem with the PRV, and you should contact a Gas Safe registered engineer to check and replace the valve. 

What to do if you suspect a faulty PRV:

• Check the boiler's pressure gauge: Ensure the system pressure is within the correct range, typically between 1.0 and 1.5 bar.

• Repressurise the system: If the pressure is low, use the filling loop to add water until the gauge shows around 1.5 bar, then reset the boiler.

• Monitor the system: If the F22 code reappears and you continue to see water dripping from the external overflow pipe or the pressure drops again quickly, the PRV is likely faulty.

• Call a professional: For a faulty PRV, you should contact a Gas Safe registered engineer. They will be able to safely inspect, repair, or replace the component. 

Why a faulty PRV causes an F22 code:

• The pressure relief valve is a safety component designed to release excess pressure if it builds up too high.

• If the valve is faulty, it can release pressure unnecessarily, causing the system's water pressure to drop below the required level.

• This low-pressure condition is what triggers the F22 fault code on your Vaillant boiler.