You are thinking of section 250.104 of NFPA 70, the National Electrical Code published by the U.S.A. National Fire Protection Association. (-: BS 7671 (IEE Wi

You are thinking of section 250.104 of NFPA 70, the National Electrical Code published by the U.S.A. National Fire Protection Association. (-: BS 7671 (IEE Wiring Regs) does not require bonding of the pipework if the mains (service) pipes and the internal (installation) piping are both plastic.