If a  F22 message appears on the boiler you will have no heating or hot water. This is not usually because the central heating system has lost some pressure (a little bit of water). It is nothing to be concerned about unless it happens regularly, if it does then it may be a boiler fault or a leak on the central heating system. Lots of systems will need filling 3 or 4 times a year. Adding pressure or filling is simple and most home owners will do it themselves. Please follow these steps if you feel confident. First have a look around the central heating system and boiler for signs of water, if none are present then proceed.

TIP: if you press any of the 4 buttons under the screen it will light up blue for a while to make it easier to see.

Under the boiler you will find 2 levers with the word “closed” on them. Please turn the lever on the right, it will only turn 1 way, it will turn ¼ turn then it will stop.

Now carefully turn the valve on the left, you will hear a hissing sound of the water and pressure being added to the system. It’s important to do this slowly and keep looking at the screen because it is best not to put too much in.

On the screen you will see the pressure going up, once there is the minimum pressure the display will change.

In the centre of the screen a none flashing number will appaer when the minimum pressure is in. This number is not important, on the right hand side you will see a graphic with bar on top. Some of this is filled in, you will see a dotted line towards the bottom and the same near the top, keep adding pressure until you are around 30% full. DON’T FILL ALL THE WAY TO THE TOP.

Finally turn the valves back to the position they stated in (across the pipe). The heating and hot water will now work normally.


Why does this happen? The boiler has a water pressure sensor, this is to make sure the boiler doesn’t start if there is no water inside it which could damage the boiler. When water (pressure) is lost from the boiler or central heating system a F22 fault is triggered. It is possible that it’s a boiler fault, (the boiler is leaking) or in an older boiler it could be the expansion vessel has failed. On a new boiler it is most likely caused by a leak on the central heating system. If you have to add water to the system every few days or even once a week the leak needs to be found and repaired. Ingnoring this and adding pressure too often and you will lose all of the inhibitor within the radiators which can cause sludge to build up, this would be damaging to the boiler. Also damage could be caused to your property.