A valve unit for pumps comprising: - an inlet conduit, - a first chamber communicating with the inlet conduit, - a second chamber communicating with the first chamber via a first valve seat, - an outlet conduit communicating with the second chamber, - a first obturator body housed within the second chamber and movable between a closed position, wherein it closes the first valve seat, and an open position, wherein it opens the first valve seat, - a first resilient element adapted to push the first obturator body towards the closed position in contrast with the pressure present within the first chamber, - a discharge conduit communicating with the first chamber via a second valve seat, - a third chamber communicating with the second chamber and partially defined by a sliding plunger, - a second obturator body rigidly connected to the plunger and housed in the first chamber where it is movable between a closed position, wherein it closes the second valve seat, and an open position, wherein it opens the second valve seat, and - a second resilient element adapted to push the second obturator body towards the closed position in contrast with the pressure present within the third chamber, characterized in that it further comprises: - an internal cavity obtained in the second obturator body and communicating with the first chamber, - a connection conduit obtained in the second obturator body, which is in communication with the discharge conduit and in communication with the internal cavity via a third valve seat, - a third obturator body housed within the internal cavity of the second obturator body and movable between a closed position, wherein it closes the third valve seat, and an open position, wherein it opens the third valve seat, and - a third resilient element capable of pushing the third obturator body towards the open position in contrast with the pressure present in the first chamber. - an inlet conduit, - a first chamber communicating with the inlet conduit, - a second chamber communicating with the first chamber via a first valve seat, - an outlet conduit communicating with the second chamber, - a first obturator body housed within the second chamber and movable between a closed position, wherein it closes the first valve seat, and an open position, wherein it opens the first valve seat, - a first resilient element adapted to push the first obturator body towards the closed position in contrast with the pressure present within the first chamber, - a discharge conduit communicating with the first chamber via a second valve seat, - a third chamber communicating with the second chamber and partially defined by a sliding plunger, - a second obturator body rigidly connected to the plunger and housed in the first chamber where it is movable between a closed position, wherein it closes the second valve seat, and an open position, wherein it opens the second valve seat, and - a second resilient element adapted to push the second obturator body towards the closed position in contrast with the pressure present within the third chamber, - an internal cavity obtained in the second obturator body and communicating with the first chamber, - a connection conduit obtained in the second obturator body, which is in communication with the discharge conduit and in communication with the internal cavity via a third valve seat, - a third obturator body housed within the internal cavity of the second obturator body and movable between a closed position, wherein it closes the third valve seat, and an open position, wherein it opens the third valve seat, and - a third resilient element capable of pushing the third obturator body towards the open position in contrast with the pressure present in the first chamber.