Trying to find the name of this Horror Movie

So I don't remember much about this film and its driving me nuts trying to find it. I remember that it is about a handful of teenagers coming off a prom or dance of some sort. They decide to whoop it up in this creepy house. Then suddenly a group or family of deformed or mutated people come out and start killing everybody one by one. The most significant scenes I remember are a guy gets badly sliced, like no legs.... and he's crawling through an air duct hiding/looking for help. Then another guy decides to run for it and gets caught by a bear trap.... and I remember one girl gets drowned in a bathtub.
I can't place any of the faces as famous people I recognize so it may have been a low budget campy B movie, but if anyone has the slightest idea please give me a shout.