the cleaning system according to the invention can be used for adjusting the ph value of the liquid near the wall of the process pipe or structures installed inside the pipe so that the precipitations can fasten to them fig2 shows a solution for arranging the reactor according to another preferred embodiment of the invention into the flow pipe in the solution of the figure the reactor is positioned between two pipe elbows 32 and 34 so that the electrode rod 16 can be supported by its ends to the pipe elbows and to arrange a support by arms 14 only when needed either by one arm arrangement to the middle part of the reactor or by a number of arm arrangements along the electrode rod 16 in this embodiment the support arms 14 of the electrode rod located in the reaction zone of the reactor are preferably either fully made of or at least coated with a material to which the carbonate particles do not fasten to as the electrode rod 16 extends in the embodiment of the figure to the outside of the pipe elbow 34 of the reactor the electrode rod can be connected straight to the control unit without the need to direct the conductor via the support arm to the electrode rod inside the reactor in this case the electrode rod 16 is isolated from the flow pipe i e the reactor.