PEX plumbing is a type of plastic tubing made from high-density polyethylene. Besides being the newest player in the water supply line game, PEX is also used for radiant floor heating tubing. What Is PEX Plumbing? You’ve probably seen rolls of blue and red PEX pipe in the plumbing aisle of your local home improvement store, but you might not know that this colorful tubing now makes it...