Are all grey flexible water lines polybutylene? I have found some that do not have the PB 2110 label, but look the same. Qest and Vanguard are two of the labels found on these products. I am getting conflicting opinions from Plumbers and General Contractors as to wether these products are problematic or polybutylene. Vanguard pipe and fittings Ltd states they never manufactured a polybutylene product but Vanguard Tubing in Witchita did. It appears Qest also did. Just trying to figure out what products (that do not carry the PB stamp) should be flagged as problematic. One plumbing contractor states ALL grey flexible tubing is polybutylene.