Not sure what the lines under the sink are made of to tell you the truth. I never paid any attention. If it's the ones I'm thinking of, then I think it's pvc, but I'll have to ask hubby on that.

I don't think the problem is my sink lines though because the water is like that at my mom's house, at my workplace, and at hubby's workplace (which is newer than all of them). I'm thinking our city just has cruddy tasting water.