I have an Alfa 147 and when I fill the washer bottle within an hour or so it drains completely, it seems like it's draining from the headlamp washers. I'm completely new to this so any thoughts will be gratefully received
There is an anti-syphon valve in the headlamp washer line that can seize or let by, IIRC it will be found behind the bumper.
If you don't fancy taking it all apart you can simply insert any cheap one way valve in the outlet line from the washer tank, can be sorted in less than 10 minutes.
Just out of interest have you checked the sprayers on the bonnet? Mine were loose and the water trickled down bonnet and appeared as a pool at the front of the car. The underneath of the bonnet will feel damp..