Fixing the Vaillant F22 Error Code
The Vaillant F22 error code indicates that your boiler has low water pressure. This is a common error code that many homeowners encounter with their Vaillant boilers. When the F22 error displays, it means the water pressure inside the boiler has dropped below the minimum level required for safe operation. Left unresolved, low water pressure can lead to a lack of hot water and heating from your boiler.
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Fortunately, in most cases, fixing the F22 error is straightforward – you simply need to increase the water pressure back to the optimum level. This article provides a step-by-step guide to increasing boiler water pressure and resolving the Vaillant F22 error code.
What Causes the Vaillant F22 Error Code?
Before diving into how to fix the problem, it helps to understand what causes low water pressure and the F22 error in the first place.
Here are some of the most common reasons why your Vaillant boiler may display the F22 code:
- Small leak in the heating system – If there is a tiny leak in one of your heating pipes, radiators or other components, water will gradually escape leading to lower system pressure.
- Faulty automatic air vent – All boilers have auto air vents to release trapped air. If stuck open, these can slowly reduce water pressure.
- Expansion vessel failure – The expansion vessel maintains pressure through heating/cooling cycles. If damaged, pressure is lost.
- Loose or faulty connections – Any areas where water pipes connect to components can leak if not fully tight. This includes service valves.
- Boiler/system drain valves left open – Drain valves may have been left open after maintenance or draining down the system for summer.
- Boiler pressure gauge issue – In some cases, the pressure gauge itself may be providing an incorrect low reading when the system pressure is actually normal.
In most situations, the problem is a small system leak or component failure allowing water to escape and pressure to reduce gradually over time.
Step-by-Step Guide to Fixing the Vaillant F22 Error
Fixing low water pressure is carried out by topping the system back up to the correct level. This pressurises the boiler and heating system to the optimum level for safe function.
Here is a step-by-step guide to increasing boiler water pressure and resolving the F22 error code:
Step 1: Locate the Filling Loop
The first step is to locate the filling loop. This is a small device fitted to all heating systems that allows you to top up water pressure.
On Vaillant boilers, the filling loop is usually located directly underneath the boiler itself. It may also be positioned nearby, attached to heating pipework.
The filling loop consists of two isolation valves with a silver braided flexible hose between them. By opening both valves, the filling loop allows new water into the system from the mains water supply.
The filling loop has two valves that must both be opened to allow water in
Step 2: Open Both Valves
With the filling loop located, open both isolation valves fully in an anti-clockwise direction. You should immediately hear water flowing into the system.
If the valves are stiff, give them a tap or twist to loosen before opening. Make sure both valves are fully open so water can flow unobstructed.
Turn both fill loop valves fully anti-clockwise to the open position
Step 3: Watch the Pressure Gauge
Keep an eye on the pressure gauge as the system fills. This is usually located on the front of the boiler.
The pressure should begin climbing back up into the green normal operating range.
For Vaillant boilers, the optimum pressure is between 1 and 1.5 bar when cold. Other boiler makes may vary slightly – check the instruction manual for the exact figure.
Allow pressure to rise to between 1 and 1.5 bar
Step 4: Close Valves Once Correct Pressure Reached
As soon as the pressure gauge indicates between 1 and 1.5 bar, turn both fill loop valves clockwise to close them.
This stops further water entering the system. Double check the pressure gauge remains in the green zone and is not still rising.
If the needle exceeds the green section, release a little pressure by opening the relief valve nearby until it drops back down.
Close both valves fully once target pressure is reached
Step 5: Check for Leaks
With the system re-pressurised, check the entire boiler and all visible pipework for any leaks.
Wipe all connections and joints with a cloth to remove any water. If leaks are present, you should see new droplets forming.
Typical areas to check include:
- Cold water inlet and outlet pipes
- Condensate trap and pipe
- Pressure relief valve and discharge pipe
- Heating flow and return pipes
- All threaded joint unions and connecions
If leaks are spotted, isolate the boiler and contact a heating engineer to resolve.
Step 6: Reset and Restart Boiler
Providing no leaks are seen, restart the boiler to resume normal operation.
On the boiler front panel, press the reset button. This may be labelled as “Reset” or have a circular arrow icon.
The boiler will then go through an automatic restart sequence. Check the pressure gauge remains in the optimal zone while operating.
The F22 error should now be cleared, and hot water and heating restored. If not, the problem may require investigation and maintenance by an engineer.
Why is Correct Water Pressure Important?
Maintaining the optimum water pressure is essential to ensure a boiler operates safely and efficiently.
There are two key reasons why the pressure must be kept between 1 and 1.5 bar:
1. Prevent Boiler Damage
If pressure drops too low, water in the boiler can boil rapidly causing intense heat and stress on components. This can lead to warping, fractures and premature failure.
2. Allow Circulation
The water pressure enables circulation around the heating system and through radiators. Low pressure may prevent hot water and heating reaching the radiators.
So in summary, the green operating pressure ensures safe temperatures inside the boiler and provides the head needed to drive water flow around the full system.
What if Re-Pressurising Doesn’t Fix the F22 Error?
In most cases, topping up the system pressure resolves the low pressure issue and clears the F22 error code. However, if the error persists, there may be an underlying fault causing recurring pressure loss.
Potential causes include:
- Leaking diaphragm or seals on the expansion vessel
- Small leaks inside the boiler on internal components
- Sticking pump unable to maintain pressure
- Defective pressure sensor providing false low readings
Where the F22 error continues after topping up the system, a Gas Safe registered engineer will be required to attend and diagnose the fault.
An experienced boiler professional will have the skills and equipment to fully test components and identify any issues. They can then carry out the required repair or replacement of parts to resolve the problem permanently.
Ongoing low pressure and the F22 error could lead to permanent boiler damage if left unchecked. So the underlying problem needs to be resolved before your next annual service to prevent future issues.
Conclusion: Resolving the Vaillant F22 Error Code
The Vaillant F22 error code indicates your boiler water pressure has dropped too low for continued safe operation.
In most situations, this can be fixed easily by locating the fill loop and topping up the system back to between 1 and 1.5 bar pressure.
Keep an eye for any leaks once re-pressurised and restart your boiler. This should clear the F22 error and restore normal heating and hot water function.
However, if the error continues to occur, have your boiler and system checked by a qualified engineer to identify and resolve the underlying fault.
Catching low pressure issues early and understanding how to top up the system can help keep your boiler running reliably for years to come. But don’t hesitate to call an expert for assistance if problems persist after following these steps.