Earthing is used to protect people from the risk of electric shock. If the earthing arrangements within your electrical installation are defective or inadequate, you run a severe risk of receiving an electric shock or burn from equipment or an appliance metal casing. Electrical shocks can be fatal.

The purpose of earthing is to provide a path for electric fault current to flow safely to earth to enable the circuit breaker or fuse to operate.

Bonding is the connection of incoming metal water and gas pipes to the main installation earthing terminal and is vital to providing you protection from electric shock.

Supplementary bonding is often found in bathrooms or any other room containing a bath or shower. The purpose of supplementary bonding is to reduce the risk of electric shock where people may simultaneously touch two separate metal parts, such as radiators and water pipes, when an electrical fault occurs in the electrical installation.

In a correctly earthed installation, any appliance developing an earth fault will be quickly disconnected by the operation of the circuit fuse or circuit breaker.

In a bathroom/showeroom, supplementary protective bonding conductors connect together the circuit protective conductors of electrical equipment. For example, an electric shower to hot and cold metal water pipes and any metal radiators or towel rails.

The above arrangements were common on installations up to June 30^th 2008. However, the introduction of new IEE Wiring Regulations BS7671 (2008), after this date, has reduced the need for supplementary bonding as all electrical circuits and equipment (excluding SELV) must be additionally protected by a 30mA RCD.