Prepared by PPI’s Building & Construction Division, PPI TN-31Differences Between Crosslinked Polyethylene (PEX) and Polybutylene (PB) Piping Systems for Potable Water Plumbing Applications discusses the advantages of modern PEX tubing and fittings as compared with PB tubing and fittings, which were last sold in the U.S. during the late 1990s.