of PEX in all occupancies. An environmental impact report and subsequent studies determined there were no causes for concerns about public health from use of PEX piping. Government approvals PEX has been approved for use in all fifty states of the United States as well as Canada, including the state of California, which approved its use in 2009. California allowed the use of PEX for domestic water systems on a case-by-case basis only in 2007. This was mostly due to concerns about corrosion of the manifolds (rather than the tubing itself) and was allowed to be used in California for hydronic radiant heating systems but not potable water. In 2009, the Building Standards Commission approved PEX plastic pipe and tubing to the California Plumbing Code (CPC), allowing its use in hospitals, clinics, residences, and commercial construction throughout the state. Formal adoption of PEX into the CPC occurred on August 1, 2009, allowing local jurisdictions to approve its general use, although there were additional issues, and new approvals were issued in 2010 with revised wordings to the 2007 act. Alternative materials Alternative plumbing choices include: Aluminum plastic composite are aluminum tubes laminated on the interior and exterior with plastic layers for protection. Corrugated stainless steel tubing, continuous flexible pipes made out of stainless steel with a PVC interior and are air-tested for leaks. Polypropylene Pipe, similar in application to CPVC but a chemically inert material containing no harmful substances and reduced dangerous emissions when consumed by fire. It is primarily utilized in radiant floor systems but is gaining popularity as a leach-free domestic potable water pipe, primarily in commercial applications. Polybutylene (PB) Pipe is a form of plastic polymer that was used in the manufacture of potable water piping from late 70's until 1995. However, it was discovered that the polyoxymethylene (POM or Acetal) connectors originally utilized to connect the polybutylene tubes were susceptible to stress enhanced chemical attack by hypochlorite additions (a common chemical used to sanitize water). Degraded connectors can crack and leak in highly stressed crimped areas, causing damage to the surrounding building structure. Later systems containing copper fittings do not appear to have issues with hypochlorite attack, but polybutylene has still fallen out of favor due to costly structural damage caused by earlier issues and is not accepted in Canada and U.S. PEX-AL-PEX PEX-AL-PEX pipes, or AluPEX, or PEX/Aluminum/PEX, or Multilayer pipes are made of a layer