Maybe the plumber forgot to put G/Y identification markings on the piece of waterless pipe which was 'bonding' the two adjacent ones?They got the plumbers to 'ream out' copper T pieces and slip them over the pipe then run a piece of pipe to the adjacent pipe, ie this linked 2 pipes together without a water connexion and still the inspectors of the time wanted to see earth clips doing the same job.
Kind Regards, John