Hydraulic valve for dual-flush toilet flush, comprising: a casing intended to be combined with a passage for draining water from the toilet flush, a tubular element at least partly housed and movable in said casing and having a first end portion and a second end portion in fluidic communication with each other and each having at least one respective opening (6, 7), a gasket integral with said first end portion of said tubular element and substantially perpendicular to the latter, for the closing and opening of the passage for draining water, movement means intended to be combined with activation means operated by a user, which movement means are active on said tubular element for its displacement between a resting position corresponding to the aforesaid closing and at least one first water draining position and a second water draining position which correspond to the aforesaid opening, a caisson-like element combined with said casing at an end portion thereof on the side of said first end portion of said tubular element, and a movable rod-like element extended in said casing and substantially parallel to said tubular element, characterised in that, in said resting position and in said first draining position, said rod-like element locks said caisson-like element, wherein, in said second draining position said caisson-like element, free from said rod-like element and subject to floating, locks said tubular element, said movement means being active on said rod-like element at the exceeding of a preset displacement of said tubular element, for a displacement of said rod-like element from a position of interference with said caisson-like element to a position of no-interference with said caisson-like element, said valve further comprising restraining means acting on said rod-like element in said position of no-interference with said caisson-like element, and restoring means integral with said tubular element at said second end portion thereof and acting on said rod-like element to restore said position of interference of said rod-like element with said caisson-like element, wherein said movement means act on said restoring means. a casing intended to be combined with a passage for draining water from the toilet flush, a tubular element at least partly housed and movable in said casing and having a first end portion and a second end portion in fluidic communication with each other and each having at least one respective opening (6, 7), a gasket integral with said first end portion of said tubular element and substantially perpendicular to the latter, for the closing and opening of the passage for draining water, movement means intended to be combined with activation means operated by a user, which movement means are active on said tubular element for its displacement between a resting position corresponding to the aforesaid closing and at least one first water draining position and a second water draining position which correspond to the aforesaid opening, a caisson-like element combined with said casing at an end portion thereof on the side of said first end portion of said tubular element, and a movable rod-like element extended in said casing and substantially parallel to said tubular element, characterised in that, in said resting position and in said first draining position, said rod-like element locks said caisson-like element, wherein, in said second draining position said caisson-like element, free from said rod-like element and subject to floating, locks said tubular element, said movement means being active on said rod-like element at the exceeding of a preset displacement of said tubular element, for a displacement of said rod-like element from a position of interference with said caisson-like element to a position of no-interference with said caisson-like element, said valve further comprising restraining means acting on said rod-like element in said position of no-interference with said caisson-like element, and restoring means integral with said tubular element at said second end portion thereof and acting on said rod-like element to restore said position of interference of said rod-like element with said caisson-like element, wherein said movement means act on said restoring means.