Vaillant F22 Fault Code - How to fix?
What does the Vaillant F22 Fault Code mean?
The F22 Fault Code, aka F22 Error of the Vaillant and the Vaillant Eco-Tec, means that the boiler is low on water pressure and needs to be re-pressurised to work again.
Causes of the F22 Error: low water pressure
F22 Safety switch-off: Low water pressure: No/insufficient water in the product or the water pressure is too low.
- Check: Plug, cable to heating pump or water pressure sensor, water pressure sensor, heating pump.
- Activate and purge check programme P.0.
What should the water pressure be on a Vaillant boiler?
Like most pressurised boilers a Vaillant boiler will only work when it has the required internal water pressure, which should be 1 bar, read as about 10 o’clock on the pressure gauge when the system is cold.
Fluctuations of the water pressure on a boiler
Expect the fluctuations to be between 1 bar from cold up to about 2 bar when hot with the heating running for an hour or so, readings outside of these parameters ie below 1 bar or above 2 bar, are not uncommon but they might point to a potential fault developing and you should book an annual boiler service with a Gas Safe registered heating engineer to prevent a possible boiler breakdown.
Vaillant F22 Error Code: Common Causes
In rare cases the PCB or the pressure sensor can fail to register the correct pressure and give an incorrect fault. You can check your analog gauge on the front of your Vaillant boiler, if this indicates that there is pressure in the boiler.
If you’re still seeing an F22 error code it’s best to call a Gas Safe registered engineer to investigate further.
In most cases the F22 fault will be correct and you’ll notice the gauge reading zero, this means your system has lost pressure.
There are unfortunately lots of reasons why a boiler will lose pressure. Boilers will commonly lose pressure once or twice a year due to air being released through vents or tiny weeps on the old pipework. If you need to increase the pressure in your boiler more frequently, anything from daily to once every couple of months, it indicates you have a more severe fault and a Gas Safe registered engineer will be needed to investigate further.
Try to find what’s causing the low pressure in the boiler
If the system looks OK, one of the boiler parts could have failed, the air vent, the pump and the diverter valve in Vaillant boilers can all leak and cause the pressure to drop. Another common cause is the expansion vessel failing causing the PRV to discharge and subsequently continue to drip.
Fixing the Vaillant Boiler F22 Fault
Once the boiler and system are cold the first thing you’ll need to do is find the charging link, better known as the filling loop:
- On a Vaillant ecoTec boiler you’ll have two grey, plastic knobs directly underneath the boiler which will stay closed on them, turning these knobs will allow water to flow into the heating system and increase the boiler pressure.
- On other Vaillant boilers and other boiler manufacturers the filling loop will look like a grey, mesh, flexible hose which connects two pipes together: it’ll usually be below the boiler, in the cylinder cupboard or sometimes below the sink or behind the washing machine.
Whatever type of filling loop you have, you must remember to close the valves and never charge the boiler past 1 bar, this could cause further damage elsewhere in the system and boiler.
Once you have re-pressurise the boiler, you might need to reset the boiler to clear the F22 fault by holding the reset button for 5 seconds.
The boiler stopped working for a reason
Remember, even if the boiler has fired, it stopped working for a reason and a professional Gas Safe registered engineer is the only person who pinpoint exactly why and ensure your Vaillant boiler is operating safely.