sterile or tap water for meds?

When giving meds through a NG tube, peg tube, DHT, whatever....do you use sterile water or tap water?
I have always used tap water until I started a new job where they use sterile water. This is strange to me. I was told tap water has contaminants that aren't good for our already at risk patients. Is this true?

I drink tap water. Do hospitals have a special kind of tap water that isn't drinkable?? I've never known anyone to drink sterile water, I can't remember why it's bad for you, but it is right?

Thanks