glowworm 24ci

Hello, This is my first time posting on here and I am a complete novice with boilers so any help is much appreciated. I have noticed a leak coming out of the bottom of my Glowworm 24ci boiler - it is dripping once every 10-15 seconds. I took a look and couldn't see exactly where the leak was...

Drips about half a saucer per day - but enough to lose pressure and need topping up every couple of days. Anyone can tell me what this component is? Is it possible to 'adjust' this component i.e. stop it dripping - or it needs replacing?