Extract from AS/NZS 3019:2007
3.2 Inspection requirements
(b) The exposed portions of the earth electrode show no evidence of corrosion, damage or poor connection of the main earthing conductor;
(c) Metallic water pipe has not been replaced with plastic piping when the piping is used as the earth electrode.
4.4 Main earthing conductor
(a) The main earthing conductor is the correct size;
(b) The main earthing conductor is connected to the earth electrode by a suitable corrosion-resistant connection;
NOTE - In installations prior to 1976, metallic water pipe may have been used as the earth electrode. Recent work practice in the water supply industry has been to replace metallic pipes with non-conductive pipes. It is recommended that an earth electrode be installed in such installations.
(c) The main earthing conductor terminations are accessible;
(d) Connections are mechanically sound and fixed by a secure system;
(e) Connections are protected against mechanical damage, corrosion, and any vibration likely to occur;
(f) Connections do not impose any appreciable mechanical strain on the component fittings of the connection;
(g) The main earthing conductor is correctly connected at the main switchboard; and
(h) Required labelling of the main earth connection is correct.
4.7.1 Earth continuity tests
(a) The main earthing conductor between the main switchboard and the earth electrode is continuous and the resistance of the main earthing conductor does not exceed 0.5 ohms.