The system has a connection block (1) inserted in a main supply line, and a main supply passage channel (3) forming a section of the main supply line. A flow block (4) is inserted in a borehole of the connection block, in right angle to the main supply passage channel. The flow block comprises secondary passage channels (13, 14), at which a secondary line is connectable, and a flow resistance body (9) e.g. orifice plate, that extends in to the main supply passage channel. The main supply line is made of plastic or virginia steel.
