It sounds like he's gotten into a habit, no matter what ye do, he's always gonna aim for his water, other than the advice of hiring the water, right out of aims way, look to what hight he pisses and up it a few inches, nothings gonna stop him, it's habit now, thats just the place to piss!
Could be worse though, i've got one that makes a bee line for my other dog, when he's stopped for a sniff, and pisses right on his head, the poor 'ol buggers only got one eye an usually don't see it coming, ends up with an eye socket filled up to the brim.... Nasty!