PEX tubing ranges in size from imperial sizes of 1/4-inch to 4-inch, but 1/2-inch, 3/4-inch. I am used to copper and PEX just doesn't look like plumbing to me and under control so it looks like it wasn't installed by a bunch of day laborers. I sort of got exhausted in asking a bunch of people. is the leading online supplier of Radiant Heat, Hydronic Heat, & PEX Plumbing Supplies. Our Radiant Floor Heat Products include PEX Tubing.