In a domestic electrical installation there should be a Main Earth, Main Equipotential Bonding and Supplementary Equipotential Bonding. The idea is to protect all the pipework and metalwork in the house, so that in the event of a fault occurring, the fuse/MCB will disconnect within the regulated time (usually 0.4 of a second).
It is quite common to have gas safety certificates to flag supplementary equippotetial bonding as a defect or ‘not current standard’.
Supplementary equipotential bonding
This is bonding for the hot water and the central heating – It is “Cross bonded” by attaching 4mm green & yellow cables to each of the pipes in the bath/shower room or in the airing cupboard if it adjoins, or is in the bath/shower room. The bath/shower room is the most important place to be bonded, as this is where you could be wet, naked and vulnerable to electrocution. All metalwork in these areas must be bonded.
Main equipotential bonding This is usually a 10mm green & yellow cable, which runs from the consumer unit to the house side of the main water stopcock and to the house side of the gas meter. These are necessary nowadays as the water and gas service providers run their supplies in plastic pipes and so there is no longer a “Good earth” from their pipes. Your inspection certificates would still pass with these defects listed as they are not life threatening, however most councils and housing associations will not accept a inspection report with these types of defects. We can carry out Earth Bonding on your property for only £60.