remove n/s lower plastic fascia [2 screws at bottom,one plastic rivet type fitting at top adjacent to door,then top pulls from its fixings] pull straight so you dont break top fixings. you should be able to see water valve and feed pipes,metal feed pipe connector and water valve are prone to leaking on this vehicle!
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix vans.