Supplementary bonding is done using minimum 4mm2 Earthing cable ( green and yellow) and involves making a safe equipotential zone, this is normally in the bathroom. The rules for supplementary bonding in kitchens has been relaxed and there is no specific requirement to carry out supplementary bonding in domestic kitchens, wash rooms and lavatories that do not have a bath or shower. That is not to say that supplementary bonding in a kitchen or wash room is wrong (it would be wrong for plastic pipes) but it is not necessary.

All electrical pages are for information only! New rules have been introduced for electrical safety in the home, please read this document by clicking here, before starting any electrical work


Before working on any electrical circuit you must ensure that it is isolated correctly and cannot accidentally be switched back on. Please read the article on safe isolation procedures before doing any electrical work. If you are not 100% certain what you are doing call a qualified electrician. Building regulations are changing all the time and modifying your home electrics could be against new rules and could invalidate your home insurance, if in doubt check first!


In a bathroom all metal pipes and all electrical items require supplementary bonding, so the light needs bonding to the metal pipe work, this includes a separate earth clamp on each pipe beneath the Basin and bath, the central heating pipes, the pipe to the shower and the shower itself (if electric) any shaver sockets or other electrical outlets also need bonding to the metal pipe work to create a safe equipotential zone. This is not as difficult as it sounds because you do not need to use a individual wire for each earth clamp, you can use one single wire as long as you do not cut it. Details of how to achieve this are in the connecting earth wire section below. Please note that with the latest 17th edition IEE wiring regulations it may no longer be necessary to install supplementary bonding if all circuits in the home are RCCD protected, please check with a qualified electrician.



supplementary bonding

Cold water pipe


 Hot water pipe

 Earth clamp, with safety Label

Central heating pipes



cross bonding

If you have an airing cupboard and hot water cylinder, the metal pipes may need supplementary bonding together.

cross bonding water tank

If you have any plastic water tanks then to provide continuity of earth it is essential that the metal pipes entering and exiting the tank are Bridged with clamps and minimum 4mm2 earthing wire.