Any person supplying or permitting the supply of gas through a primary meter to a secondary meter shall ensure that a line diagram in permanent form is prominently displayed on or near the primary meter or gas storage vessel and on or near all emergency controls connected to the primary meter showing the configuration of all meters, installation pipework and emergency controls.
Any person who changes the configuration of any meter, installation pipework or emergency control so that the accuracy of the line diagram referred to in paragraph (1) is affected shall ensure that the line diagram is amended so as to show the altered configuration.