Where the service pipe to any building having two or more floors to which gas is supplied or (whether or not it has more than one floor) a floor having areas with a separate supply of gas has an internal diameter of 50 mm or more, no person shall install any incoming installation pipework supplying gas to any of those floors or areas, as the case may be, unless—
indicating the position of all installation pipework of internal diameter of 25 mm or more, meters, emergency controls, valves and pressure test points of the gas supply systems in the building.
Paragraph (1) above shall apply to service pipework as it applies to a service pipe except that reference therein to "50 mm or more" is to be reference to "30 mm or more".
In paragraph (1)(b) above "pressure test point" means a gas fitting to which a pressure gauge can be connected.