The use of PEX (cross-linked polyethylene) tubing has become common in radiant floor heating systems. Although PEX manufacturers have also been promoting the plastic tubing for domestic hot and cold water pipes, the use of PEX for such potable water pipes is still relatively rare. According to the March 2001 issue of the plumbing magazine Reeves Journal, 89.6% of surveyed plumbers said that copper is the piping material they most frequently install for new potable water distribution, versus only 7% who usually install PEX. In some areas of the country, the preference for copper is even stronger. “Close to 98 percent of the pipe we sell for potable water is copper,” says Kevin Morrison, outside salesperson at F.W.