Abstract: Method for the prevention and/or removal of biofilm and sediment formation in borehole tubes or distribution tubes, with the following steps: (i) mounting one or more ultrasonic transducers (9, 9?) on an aboveground part of the tube; (ii) sending the ultrasonic waves whereby both the power and the frequency of the ultrasonic waves are varied in time, with a frequency between 20 and 60 kHz and a power between 1 and 6 Watt for smaller tubes and between 6 and 40 Watt for larger tubes; (iii) sending the varying ultrasonic waves through the water that flows or is pumped through the tube; (iv) providing an automatic interruption of the effect of the ultrasonic waves when the flow of the water through the tube stops, either by shutting off the transducers, or by the automatic operation of a non-return valve which interrupts the water column between the transducer and the underlying mass of water.