Real quick IV question

]I was floated to Acute HealthCare/Stepdown, last night from my home floor, Orthopedics. I've been to stepdown before. But anyway.......I'm just baffled by how each floor seems to do certain things different ways. I havn't been a nurse but for 2 years, in the hospital for 1 of them, so please forgive me if this question seems dumb.

I had a pt on a heparin drip...and when I went into the room, she had one iv site, with heparin at 20cc/hr and NS going at kvo, and the previous nurse had been using that same site for Ancef PB and also for her demerol/phenergan prn. I was cofused and called pharmacy, because I had always known and been told that heperin should always be a separate site. Pharmacy said it was ok as long as the Ancef was Y'd in....ok fine. But what about the NS at kvo...all it is doing is diluting the heparin isnt it? And then giving the demerol and phenergan thru the same line? I went ahead and did it my way by getting a separate line...but everyone on that floor said that they do that all the time?? Should you really?