Piping used for transporting high purity water must receive equal quality considerations. Suitable materials include polypropylene (PP), polyvinylidene fluoride (PVDF), polyethylene (PE) and stainless steel (SS) and should not re-contaminate purified water. Plastics can be joined by various methods including the popular beadless and seamless weld method used in many pharmaceutical and electronic grade water systems. Orbital welding is preferred for stainless steel. All techniques require certified, experienced personnel adhering to strict installation guidelines. Stainless steel will require cleaning and passivation, and plastic piping should be flushed and sanitized. Sanitization methods must be material compatible.