The 5 Most Common Fault Codes for Vaillant Boilers

Vaillant boilers are known for their reliability, but even the best systems can develop faults that trigger error codes. These codes are designed to pinpoint issues early, helping homeowners and engineers address problems before they escalate into costly repairs or complete system breakdowns.

Knowing what these codes mean and how to respond can save you significant time and money. Below are the five most common Vaillant boiler fault codes, along with simple steps to resolve them quickly and prevent further complications.

F22 – Low Water Pressure

One of the most common issues is the F22 fault code, which indicates low water pressure. When pressure drops too low, the boiler won’t function properly, leaving you without heat or hot water.

Solution:

  • Check the pressure gauge—it should read between 1.0 and 1.5 bar.
  • If the pressure is low, use the filling loop. You can usually find instructions in your boiler manual.
  • If the pressure drops again, there may be a leak that requires professional attention.

F28 – Ignition Failure

The F28 fault code means the boiler has failed to ignite, often due to issues with the gas supply, a blocked flue, or a faulty ignition electrode. This typically appears when the boiler can’t detect a flame during startup.

Solution:

  • Check if the gas supply is turned on and working. If other gas appliances work, the supply is likely not the issue.
  • Check for a blocked or obstructed flue that might be preventing proper ventilation.
  • If the F28 code persists, reset the boiler. For ongoing issues, call a Gas Safe registered engineer for inspection.

F75 – Pump or Pressure Sensor Failure

This code signals a problem with the pump or pressure sensor. It happens when the boiler can’t detect pressure changes when the pump starts.

Solution:

  • Check that the pressure is within the correct range.
  • If pressure levels are normal, the pump or sensor likely needs inspection—and possibly replacement—by a qualified engineer.

F61 – Gas Valve Error

F61 indicates a problem with the gas valve, which could result from electrical issues or a faulty valve. This error needs immediate attention as it could pose safety risks.

Solution

  • Turn off the boiler and contact a Gas Safe registered engineer immediately. This is not a DIY fix—the gas valve likely needs replacement.

F29 – Flame Loss

Similar to F28, the F29 fault code indicates flame loss during operation, possibly due to an interrupted gas supply, flue blockage, or a faulty flame sensor.

Solution:

  • Ensure the gas supply is steady and check the meter for issues.
  • Inspect the flue for obstructions.
  • If the issue continues, reset the boiler and consult an engineer to inspect the flame sensor and internal components.

Fault codes can be frustrating, but they provide valuable insights into what’s wrong. While minor issues like low pressure can often be quickly resolved, others require professional help. Always ensure repairs are handled by a Gas Safe registered engineer to maintain safety and efficiency.

If you’re facing persistent boiler issues or are unsure how to resolve a fault code, don’t wait—contact a qualified heating engineer to get your Vaillant boiler operating again. By staying proactive, you can avoid costly repairs and keep your home warm all year long.