As I suggested last night, I would guess that he probably did mean plastic pipe, and that he was asking the 'standard question' as to whether, say, metal taps supplied by plastic pipe need supplementany bonding (if conditions for omiting it are not satisfied) because of the water within the pipe.If your question was actual in regards to plastic pipework rather than copper. Plastic is an insulation material and will create a barrier between any potential electrical contact between the voltage and the water contained within the pipework, should an electrical fault occur.
The standard answer to this standard question appears to be 'no' - i.e. that the water in the pipe is not considered to have adequate conductivity to require the tap (or whatever) to be treated as an extraneous-conductive-part.
Kind Regards, John