Polybutylene (PB) piping was commonly used for domestic water piping in the United States during parts of the 1970s and 1980s. Polybutylene can be identified by its gray color. Lawsuits related to fitting assembly failures caused the production of PB to stop, but the plastic tubing is still present in some homes.
PB has the same outside diameter as PEX of the same nominal size, but outside diameters differ slightly between the tubing types. This means that you should not use PEX fittings on polybutylene, but that you can use PEX crimping rings and PEX crimping tools on barbed PB connections. SupplyHouse.com offers a small selection of PEX to PB fittings in common sizes. Only the SharkBite U4008LF and U4016LF fittings do not require tools on either side. The other options have barbed PB connections and either a crimp or PEX press connection on the PEX end.
