The invention relates to an installation and a method for watering with diluted waste water in bivalent irrigation systems. According to the invention, the installation comprises an irrigation installation proper (A) provided with a drum (4) and a hose (6) which delivers water/fertilizer with a sprinkler-holder carriage (2)/a delivering pipe (3) provided with some nozzles (8), a water source (B) supplying pressurized water to the irrigation installation (A), a tank trailer (C) which conveys dejections from a purification station/mechanical separators to the irrigation installation (A), a pump (D) which absorbs the waste water from the tank (C) and injects it into the irrigation installation (A) and a control device (E) which meters the water and waste water flow rate, measures the pressure in the irrigation installation (A), in the pump (D) and in the delivering pipe (3), determines the salt concentration and the pH of the fertilizing solution and displays the speed/watering rate with a revmeter (37). As claimed by the invention, the method which uses the claimed installation consists in a stage of bilaterally delivering water into the crop, on furrows, at variable flow rate, depending on the plant necessities, by means of a delivering pipe (3) having some nozzles (8) provided with some lateral elongated slots, bilaterally placed under an angle (a) in relation to the vertical, where the nozzle (8) cross section may be modified with some shuttering slide valves comprising a rubber gasket (15) with textile insertion, a U-shaped reinforcement (16), a riveted wedge (17) and an exterior sliding plate (18) fastened on the gasket (15) by means of a screw (19) and a stage of sealing the cracks/orifices, settling the furrows by means of the installation which waters, at start, by sprinkling, by uncoupling the delivering pipe (3) and coupling a sprinkler-holder carriage (2).Invenţia se referă la o instalaţie şi la o metodă de udare cu ape uzate, diluate, în sisteme de irigaţi
