Plumbing next to a grill
If it's going to get that hot in there you should be insulating the pipe regardless. Foil and fiberglass would do. 

If it gets hot enough to damage pvc with water in it you have bigger problems. Have you ever seen the styrofoam cup with water experiment? Granted, you don't want the water in the pipes to be the only thing saving your pipes, but if the space inside the cabinet gets hot enough to melt pvc you're putting your entire home (and its occupants) at risk.