Have you got a picture of the tap? The plastic tap in my Puck is exactly the same as the one I had in 2 of my previous camper vans, both of which developed leaks around the main body area even though they were only a year or two old!!
Hairline cracks developed in the area where the flexible pipe/pipes connected to the tap body, it was obviously a design fault/weakness judging by the number of others on the VW forum that suffered a similar failure.
I'm not saying that it is your fault but those plastic taps are not built to last!