A hydraulic joint (1) introduces a box it to comprising estate (2) two rooms (21, 23) between they communicating and crossed from a tree municipal (10) connected to an user, in one of such rooms (21) being present a brace of impellers (15, 17) supplies of radial shovels (16, 18), a first impeller engine (17) being functional connected to a drive shaft and the second one, conduct (15), being associated the tree municipal (10), other room (23) acting as from delay room, the box it (2) containing a fluid action to transfer the motion of impeller engine (17) and that conduct (15). Within the box it to estate (2) an ulterior room or tank (22) connected to aforesaid two rooms (21 is present at least, 23) action successively to supply with delay the fluid in contained it to the room of delay (23) to the starter of the motor, such fluid moving themselves with an ulterior delay to other room (21) where is present impellers (15, 17).