Mains & Supplementary Bonding

[Careful_Bodger]

Hi - I hope someone can confirm my thinking on Earth Bonding.

Is it allowed to mix mains bonding with supplementary bonding, or must it be evident that individual mains bonding cable runs have been separately implemented?

More specifically, do gas and water main earth wires have to go direct to an earth block by the consumer unit ? Or can one or other be linked to nearby CH pipework, then this pipework linked via additional bonding to the earth block?

Since my gas main is close-ish to the TT Earth stake, is it possible to take the gas main earth wire direct to the stake, or must it pass to the CU earth block first (for ease of inspection, say).

Is it permissable to use a 'common sense' approach, and connect everything to everything else - or does a certain 'recipe' need to be followed?

Thanks for any responses..........and for your patience if I have I used any terminology inappropriately.

 

[dingbat]

Main equipotential bonding must be connected directly between the incoming services or structural metalwork and the main earth terminal with appropriate sized conductors for the supply characteristics. You can't rely on pipework to carry the fault current. (high resistance joints, corrosion, future replacement with plastic fittings, etc.)

The main earthing conductor then runs between the main earthing terminal (which may be inside your CU, but is often a separate block) and the earth electrode or supplier's earth terminal.

Supplementary bonding is a different thing. Its purpose is to make sure that all conductive parts in a particular area (e.g. bathroom) are at the same potential.