The purpose of having your system earthed is to protect you [the user] from electric shocks. It also ensures that all surge protection devices work. For older electrical installations that do not have RCDs or trip switches, it is important that your metal pipework is earthed. This is called equipotential bonding. Pipes connected to gas or water supplies should be connected to the earth of the electrical supply. You should be able to see a metal clamp around the pipe [usually by the hot water cylinder, boiler, gas intake, bathroom or kitchen pipes]. You should see a yellow/green cable which is either connected to an earthed socket, earth junction box or back to the fuseboard. All this is very dependent on having a earth rod. If you do not have an earth rod, all these mentioned points are … pointless.
If you have earths connected at all sockets, lights and other power outlets and no earth rod your home has no protection as there is no connection to the ground. In the event of a fault, or storm, the current MUST escape through the quickest route back to the earth. If there is no rod YOU may be the only escape route.
You can check to see if you have an earth rod by looking at your fuse board. A correct installation will show a green/yellow cable coming out of the fuseboard downwards. It should go through an external wall and continue to the ground. It will be clamped to the top of a metal pole usually 12-16mm in diameter, which is buried 1metre to 1.5 metres into the ground.
The installation of an earth rod will always be tested to make sure the connection is within the safe limits. A resistance test can be performed with the correct equipment to ensure this.
The installation of a good earth and RCDs [trip switches] is paramount to a safe electrical installation.
If you are ever in any doubt, please always consult with a qualified electrician.