Suction valve for dental treatment units , said valve being connectable through tubings to a suction system placed downstream said dental treatment unit ; said suction valve comprising: - an input conduit ; - an output conduit connectable to said suction system; - said input conduit and output conduit being preferably perpendicular; - a valve seat interposed between said conduits and ; - a diaphragm placed transversally to said conduits defining a chamber above said diaphragm; said diaphragm being mobile between two extreme positions, a first resting position wherein the diaphragm adheres against the valve seat blocking the passage of air and liquids between said input conduit and said output conduit , and a second active position wherein said diaphragm is distanced by said valve seat allowing the passage of air and liquids between said input conduit and output conduit ; - a connecting conduit provided with an entry point protruding in the output conduit for some millimeters allowing the passage of air between the chamber and the output conduit ; - an electrically controllable pilot valve , which is switched between a resting position wherein it allows the passage of environmental air to the chamber through a terminal portion of the connecting conduit embedded in the body of the suction valve comprising a first portion , a closing point and a second portion , and an active position wherein it blocks the passage of the environmental air, connecting the chamber with the output conduit through the connecting conduit ; characterized in that , at the insertion point of the connecting conduit in said output conduit , there is provided a non-return valve , preventing an input flow to said connecting conduit from the entry point and therefore the upwelling of liquids from said output conduit to said pilot valve and/or to said chamber . - an input conduit ; - an output conduit connectable to said suction system; - said input conduit and output conduit being preferably perpendicular; - a valve seat interposed between said conduits and ; - a diaphragm placed transversally to said conduits defining a chamber above said diaphragm; said diaphragm being mobile between two extreme positions, a first resting position wherein the diaphragm adheres against the valve seat blocking the passage of air and liquids between said input conduit and said output conduit , and a second active position wherein said diaphragm is distanced by said valve seat allowing the passage of air and liquids between said input conduit and output conduit ; - a connecting conduit provided with an entry point protruding in the output conduit for some millimeters allowing the passage of air between the chamber and the output conduit ; - an electrically controllable pilot valve , which is switched between a resting position wherein it allows the passage of environmental air to the chamber through a terminal portion of the connecting conduit embedded in the body of the suction valve comprising a first portion , a closing point and a second portion , and an active position wherein it blocks the passage of the environmental air, connecting the chamber with the output conduit through the connecting conduit ; <EOS>