When you encounter a Vaillant Boiler F22 error, it typically indicates a low water pressure or a circulation issue within the heating system. Here's how to fix it:

1. Check Water Pressure:
   • Locate the pressure gauge on your Vaillant boiler, typically found on the front panel.
   • Ensure the pressure is within the recommended range (usually between 1 and 2 bar). If it's below 1 bar, the low pressure could trigger the F22 error.
2. Repressurize the Boiler:
   • Turn off your boiler and allow it to cool down.
   • Find the filling loop, a flexible or braided pipe that connects to the cold water supply.
   • Open both ends of the filling loop by turning the valves until they are in line with the pipe.
   • Slowly open one valve to allow water into the system, keeping an eye on the pressure gauge.
   • Close both valves once the pressure is back within the recommended range.
   • Turn the boiler back on, and the F22 error should clear if low pressure was the issue.
3. Check for Leaks:
   • If you find the need to repressurize frequently, inspect the system for any water leaks. Leaks can cause pressure to drop, leading to the F22 error.
4. Bleed Radiators:
   • Air trapped in the radiators can also lead to low system pressure. Bleed your radiators to release any trapped air. Be sure to turn off the boiler before doing this.
5. Reset the Boiler:
   • Reset the boiler by turning it off, waiting for a few minutes, and then turning it back on. Sometimes, a temporary issue can trigger the F22 error.
6. Call a Professional:
   • If the problem persists after trying the above steps, or if you are uncomfortable performing these tasks, contact a qualified heating engineer or Vaillant technician. The issue may be related to a faulty component, such as a pressure sensor or pump, which requires professional attention.

It's important to address the F22 error promptly, as low water pressure or circulation problems can impact the efficiency and effectiveness of your heating system. If you're not confident in your ability to fix the issue, seeking professional assistance is recommended.