Insulated sockets are tested to a safe live working current, for both an AC and DC electrical current. To do this they are hung from a metal rail so they are partly submerged in a bath of water. When testing to a safe working limit of 1,000 volts, 10,000 volts are passed through the water in the bath for 3 minutes. If any electrical current makes it to the metal rail from which the socket is hung, then the insulation will fail the quality control check.