have very broad meanings in this context referring to fig2 the pipe shown in fig1 is one of a plurality of identical pipes which form a pipeline 12 connecting a subterranean fuel storage tank 14 to dispensers 16 and 18 which include suction pumps not shown the pipeline 12 is inclined so that the end adjacent the dispensers 16 and 18 is higher than the end adjacent the tank 14 the pipes are contiguously arranged and where necessary may be joined together by a process of electro fusion jointing which provides leak proof joints between adjacent pipes however joints other than at manholes or in chambers are to be avoided at the upstream end of the pipeline 12 at or near the lowest point in a manhole chamber 21 above the tank 14 there is provided a leak detection sensor 20 which is situated downstream of a suction line 22 which extends into the tank 14 to allow the pumps 16 and 18 to draw fuel from the tank 14 and along the pipeline 12 fig2 also depicts a pressure line 23 which forms part of an alternative form of fuel supply system that system is known as a pressure system and uses a pump 25 at the top of the line 23 to supply fuel along the pipeline 21 in a pressure system the pump such as the pump 25 replaces the suction pumps in the dispensers 16 and 18 in this example the detector 20 comprises a reservoir not shown which communicates with the foam layers of the pipeline 12 and contains a float level.