Earth rod (pica de tierra, ground rod)

What an earth rod is

It is the part of an earthing system (grounding in the US) that makes physical contact with the ground. It is driven in vertically, by hand or by machine, and the earth cable from the installation is connected to its head. Leakage currents and overvoltage spikes disperse into the soil through it.

Where it goes

• Detached houses and villas (chalets): in the garden, a patio or an inspection pit next to the house.
• Warehouses, ground-floor premises and outbuildings: in the soil nearest the board.
• Flats: no rod of their own. The flat connects to the building earth network, buried in the foundations. If that network fails, the fix is a matter for the community.

How many you need

It depends on the soil. Damp clay conducts well and one rod may be enough. Dry, sandy or rocky ground has more resistance and needs several rods linked together and spaced apart, or a buried conductor. The way to know is to measure the earth resistance after driving the first one and add more until the value is right. In Seville, Spain, the dry summers make it wise to leave a margin.

If you have no garden

Other points can work: a pit in a garage floor, a communal garden area or drilling through paving. In a flat, the building earth network and the continuity of the conductor to your home need checking.

Price

Installing or improving earthing costs, as an estimate, 250 to 600 euros plus VAT. See earthing and, if your taps give you a shock, electric shocks from taps.