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Message: <blockquote data-quote="boltonsparky" data-source="post: 503719" data-attributes="member: 4678">Disconnect bonding conductor at MET, long lead test to the pipe/structure, not the clamp, this way you are checking the effectiveness/continuity of the connection of the clamp to pipe/structure. If there is any doubt that the bonding conductor isn't continuous or is unidentifiable at the MET and the reading you'e getting is a parallel path disconnect at both ends and perform long lead test. Very low reading you have the correct cable, an open circuit you have the other cable. You disconnect them at the MET to test to rule out the parallel paths you mention. You need to be ensuring the reading/connection is via the 10mm cable not the 1.5mm CPC of the boiler circuit. However the reading you get should confirm this anyway, the 10mm will be a much lower reading than that of a 1.5mm cpc parallel path. Anything over 0.05 ohms for a bonding conductor should be investigated. Having a reading from the MET to every accessory and piece of fixed equipment, as you mention is correct, unless they're class 2. An earth reading will be being got at sinks etc through the taps from the copper pipe work via the main extraneous bonding conductors. Disconnecting bonding conductors is still likely to get you an earth reading although a slightly higher one through the CPC of the circuit to the connection of the boiler/heating/immersion through their connection to the pipework of the house. </blockquote>

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