My guess is you are in CA or some other drought stricken area?
One other consideration is that vinyl may impart flavors while the beer is at high temps at the start of the flow. I'm not saying it WILL, just that it MIGHT.
Or, even worse, it could melt.
You would get better chilling effects by using copper, and your yeast will like it better, too.
It's far from a horrible idea, it's just that other materials for the coil would be a better choice.
Good Luck!