I have a Baxi 105he boiler installed in 2005.In the last month I noticed that I have to pressurise the boiler because it reads zero.
When the heating is running the pressure builds up to 3bars.
Can anyoe shed some light as to what might be happening?

Many thanks

Adding water to the boiler usually indicates a leak somewhere.
The safety valve might have a small leak allowing the pressuer to drop over time.

You need to check for leaks in all the pipe or the unit etc.