Ibrahim Well the other way would be to remove the thermocouple and use a syringe to remove the water. I wouldn’t personally want to be doing that.
For the service boiler I remove the anti-vacuum valve and use a syringe to get water in and out, which is what I mean by manually. The alternative, possibly easier and safer way is to drain through the hot water tap and fill using the pump and reservoir. My anti-vac valve is fitted with PTFE and is just a little more than finger tight so no risk of snapping threads off or anything - not everyone is so lucky. And I personally find it easier and less faff than emptying and refilling the reservoir, though with the Bianca that might be easier….