This safety issue has been highlighted by a number of serious electrical shocks to plumbers involved in changing water metering equipment and metallic water pipes to plastic water pipes.

The installation of plastic water pipes on the ActewAGL side of the water meter reduces the length of conductive water pipe.  Additional plastic water pipe may introduce insulated sections in the water pipe system.  This creates a water pipe system that becomes ineffective as a continuous low resistance earth return pathway to the substation. With the lessening of copper piping through the introduction of plastic piping, a high resistance earth pathway is established and may lead to inadequate earthing to the general mass of earth for the electrical installation.

This becomes a danger when the loss or partial loss of a service neutral occurs at the ActewAGL network connection to the installation's MEN point.  Any significant earth fault is returned via the earthing system rather than by the service neutral.  As a result, a potential difference is created between the metallic water pipe and other conductive surfaces or ground.  When the water pipe is in contact with earth along its length, the resistance is low and the potential difference is low and less severe.  When it is interrupted by plastic pipe, its resistance is very high, the potential is high and a danger exists to any person coming in contact with parts of the metallic water piping system.

If the metallic water pipe system within the premises is continuous, it produces are very low resistance to earth.  If earth leakage current exists within the installation and the metallic water pipes are no longer continuous through recent changeovers to plastic piping, there will be a distinct possibility that a tap, for example, connected to what was a continuous metallic water pipe earth system will develop a different potential with regards to the earth potential at the sink waste point.  There will be a fault current flow across anybody contacting the tap handle and better earthed drainage surfaces.

Plumbers are trained to connect bonding cables across the water pipe to be breached before all work is started.  Care must be taken when a plastic water pipe or insulated meter is connected to any part of the plumbing.  The metallic plumbing system must be tested to the surrounding earth and across the breach for significant voltage before any work is started.

All construction trades are warned that installed metallic water pipe work may have an electrical hazard if a tradesperson makes physical contact across the pipe breach.  The water pipe must be tested using a voltage tester to an independent or reference earth prior to the start of work.  If voltage greater than 5 volts is detected it is significant.  Call a licensed electrician to isolate supply.  The licensed electrician must contact ActewAGL and inform them of the problem.

In older areas of Canberra the metallic water pipe was electrically bonded at the point of entry into the structure and this is the essential main earth connection or plumbing bond.  This system is now out-dated and all installations should have, in addition, an earth stake installed whenever new circuits are created or a switchboard replacement occurs to the electrical installation.  Electricians will need to explain to their customer the dangers of the out-dated system.  The use of residual current devices (RCDs or Safety Switches) on existing electrical installation light and power can help to improve electrical safety.

The detection of a neutral fault can be achieved by an electrician conducting a fault loop impedance test.  This can be found in AS/NZS 3017, published in 2007.