Direct line system is the simplest type of pipeline system which uses fewer valves than the others. It takes oil directly from the tank to the pump and so reduces friction.
This has an affect of increasing the rate of discharge, at the same time improving the tank suction. It is cheaper to install and maintain than the ring main system because there is less pipeline length and with fewer valves less likelihood of malfunction.
However, the layout is not as versatile as a ring main system and problems in the event of faulty valves or leaking pipelines could prove more difficult to circumvent.The washing is more difficult since there is no circular system and the washings must be flushed into the tanks