In which case Andy, it begs the question as to why hundreds of metres of 10mm singles are thrown into installations across the land with each rewire carried out. Why bother when you can just utilise the 1.0mm/1.5mm cpc from an appliance metallic pipework to the incoming gas & water supplies!

it certainly make a difference when when pipework is truly extraneous - (either at the incoming position, or dives out underground somewhere to say an outside tap or  another building) - you really don't want large fault currents from elsewhere or diverted neutral currents on PME systems being forced down a 0.75mm² c.p.c..  But in many cases these days (with plastic plumbing) that simply can't happen - and to be fair BS 7671 definitions have supported that stance for very many years (if something doesn't meet the definition of an extraneous-conductive-part you don't have to bond it).

   - Andy.

In which case Andy, it begs the question as to why hundreds of metres of 10mm singles are thrown into installations across the land with each rewire carried out. Why bother when you can just utilise the 1.0mm/1.5mm cpc from an appliance metallic pipework to the incoming gas & water supplies!

it certainly make a difference when when pipework is truly extraneous - (either at the incoming position, or dives out underground somewhere to say an outside tap or  another building) - you really don't want large fault currents from elsewhere or diverted neutral currents on PME systems being forced down a 0.75mm² c.p.c..  But in many cases these days (with plastic plumbing) that simply can't happen - and to be fair BS 7671 definitions have supported that stance for very many years (if something doesn't meet the definition of an extraneous-conductive-part you don't have to bond it).

   - Andy.