Water Pipes as an Earthing Medium

The practice of earthing domestic electrical installation using metallic water pipes despite being included in electrical standards is a hazard which could cause possible injury, loss of life or damage to properties.

Water pipelines do not provide adequate or effective earthing due to corrosion and replacement of some portions of the piping system with plastic pipes which are not conductive.

Tap water alone does not have adequate conductivity to provide effective earthing. IEE have provided some figures on tap water conductivity on the most commonly used pipe sizes

Note: Resistance of tap water in 1 metre of plastic pipe
15 mm ɸ : 115,000 ohms;
20 mm ɸ : 65,000 ohms;

A fault on the electrical installation of a poorly earth system mean that touch potential can rise up to dangerous levels. A human in contact with the water system at the time of fault could possibly experience electrical shock causing injury or even death.

Likewise, other pipeline system within the premises will could have a higher potential than other metallic parts of the house such as sink which is also a source of another shock hazard.

To prevent possible electric shock at home, ensure that if your earthing system use the water pipeline as an earthing medium, install a separate earth rod to supplement it.