This form of piping is constructed of cross-linked polyethylene, formed into tubing for domestic water piping. PEX piping is commonly used as a replacement for, or alternative to, PVC, or copper piping. Compared to copper, PEX costs less, is quicker to install, doesn't corrode, and doesn't develop "pinhole" leaks. Compared to PVC, PEX doesn't require glue and won't burst if frozen. Because of its flexible form, PEX is easy to "fish" into walls and accommodate turns without elbow joints.