The Grundfos MP 1 pump used in the Grundfos MP 1 submersible pump sets is specially designed for purging and sampling monitoring wells with a diameter of at least 50 mm and a depth to 90 meters. The pump motor is controlled by a special adjustable frequency converter. Since the frequency is continuously adjustable, the capacity of the Grundfos MP 1 pump can be controlled from 0 to 2 m3/hour. This creates a constant flow of anaerobic water. Each new measurement must be purged before samples can be taken. The large capacity of the Grundfos MP 1 pump ensures that the measuring point is quickly purged. By setting it at a lower pumping capacity, the Grundfos MP 1 can also be used for sampling.