that has a diameter which is slightly bigger than the largest diameter of the pipe 7 i e the diameter of the ring shaped filters 9 as the clay ground 2 settles it will press rapidly i e within a few hours against the pipe 7 and thus also against the filters 9 the flow rate which flows in the chambers 8 depends on the filters 9 so that these are selected as a function of the application thanks to these filters 9 and the direct contact of the ground 2 with these filters 9 precise measurements can be obtained in various places along the borehole 3 despite possible different hydraulic fields since each of the chambers 8 is separately connected to the measuring equipment 11 and to among other things a manometer by means of conduit 10 the hydraulic pressure can be simultaneously measured in different places in the borehole 3 at the same time other parameters can be measured such as the pressure gradient and the flow by disconnecting the pipes 20 from the measuring equipment 11 samples can be taken of the water in different places in the ground 2 via the conduits 10 these places are known since the distance between the chambers 8 and thus their location on the pipe 7 is known on the basis.