In a scenario where a plastic water service pipe enters an installation, it is clearly not fit the definition of extraneous conductive part. Similar, the continuation of the service into the property , again in plastic would not be consider extraneous. When a plastic service enters a property, and continues on in metal, then a test could be made to establish if it was extraneous.
However, (I have read and been previously advised) that to conduct that test correctly, all cpc's and other possible parallel paths (like bonded gas pipes to boilers e.g.) would have to be negated, to obtain a true reading, i.e. if those cpc/bonds were removed at a later date. It is also possible, the internal service could be altered, and could be come extraneous.
Which is possibly why I seen very large numbers of plastic services, with their metal internal bonded, or is it a habit out of nature (following like sheep). Its easier to install bonding, rather than retrospectively add it, perhaps. In fact, I have always seen such bonding in place. I note that the OSG recommends bonding of metal services, after plastic, unless it has been confirmed its not introducing earth potential.
However, my previous post was not about main protective bonding, but the application of reg 528.3.4, which will require further reading and seeking guidance. Thoughts?
Sorry Tel, that's 5.