Understanding Vaillant Boiler Fault Codes: What They Mean & How to Fix Them
Vaillant boilers are known for their reliability and energy efficiency, but like any appliance, they can occasionally run into issues. Fortunately, Vaillant boilers come equipped with a fault code system that helps users and engineers diagnose problems quickly.
In this guide, we’ll break down the most common Vaillant boiler fault codes, what they mean, and what you can do about them.
Why Fault Codes Matter
Fault codes are built-in alerts that appear on your boiler’s digital display when something isn’t working correctly. Each code corresponds to a specific issue — from low pressure to faulty sensors — and helps guide repairs more efficiently.
Common Vaillant Boiler Fault Codes
F22 – Low Water Pressure
Meaning: The boiler has detected that water pressure is too low.
Fix: Check the pressure gauge. If it’s below 1.0 bar, repressurise the system using the filling loop. If the pressure drops again soon, there might be a leak.
F28 – Ignition Fault
Meaning: The boiler failed to ignite after several attempts.
Fix: Check that your gas supply is on and working. If you’ve recently run out of gas or had your meter changed, you may need an engineer to reset the boiler properly.
F29 – Flame Loss
Meaning: The boiler started, but the flame went out.
Fix: This could be due to a flue issue, gas valve problem, or a faulty electrode. It’s best to get a Gas Safe registered engineer to inspect it.
F75 – Pressure Sensor/Pump Fault
Meaning: The boiler can’t detect pressure rise when the pump runs.
Fix: Often caused by a faulty pressure sensor or a seized pump. Requires professional repair.
DIY vs. Professional Repairs
While simple tasks like topping up the pressure or resetting the boiler are safe for homeowners, most faults should be handled by a Gas Safe registered engineer. Never attempt to open or repair internal components yourself.
Preventing Boiler Faults
Annual Servicing: Keeps the boiler running efficiently and spots issues early.
Bleed Radiators: Trapped air can lead to pressure problems.
Keep Pressure in Check: Monitor your boiler pressure regularly.
Lag Pipes in Winter: Prevent frozen condensate pipes, which cause common winter faults.
Fault codes are a helpful tool — not a reason to panic. Understanding what they mean gives you more control and confidence when dealing with boiler issues.
If your Vaillant boiler displays a code you're unsure about, or you’ve tried basic troubleshooting with no luck, call a professional. The quicker a problem is diagnosed, the less chance it has to cause lasting damage.
Want to discover more error codes? Read through our dedicated Vaillant boiler fault codes page.