A circuit for supplying a liquid, in particular water, for a machine for preparing beverages, in particular coffee, said circuit comprising: - a pump for supplying said pressurized liquid into a delivery line; - a supplying area of said beverage connected to said delivery line; - a control valve for controlling the flow of said liquid between said delivery line and said supplying area; and- a heater arranged along said delivery line upstream of said valve and of said supplying area; wherein said valve comprises a hollow body, defining two paths connected respectively to said delivery line and to said supplying area, and a selection member for selectively controlling the connection between said paths; wherein said hollow body of said valve has: - a first fluid channel defining one of said paths and having a first end connected to said delivery line and a second opposite end; - a second fluid channel defining the other of said paths and having a first end connected to said supplying area and a second opposite end connected to said second end of the first channel for defining an intersection chamber between said first and second channel (51, 54); and - a seat elongated along an axis, opening into said intersection chamber at its own end and movably engaged by said selection member along said axis between an operating closing configuration, wherein said selection member closes the fluid connection between said first and second channel (51, 54), and an operating opening configuration, wherein said selection member allows the fluid connection between said first and second channel (51, 54); wherein said valve further comprises a membrane shutter housed in said intersection chamber and having a first portion locked in a fixed position inside said intersection chamber, and a second portion facing, on one side, at least one of said second ends (53, 56) of said first and second channel (51, 54), said second portion of said membrane shutter being flexible inside said intersection chamber away from and towards said at least one of said second ends (53, 56) of said first and second channel (51, 54) under the combined action of said selection member and of the pressurized liquid delivered by said pump so as to enable/inhibit the fluid connection between said first and second channel (51, 54); wherein said membrane shutter is housed inside said intersection chamber, thus dividing this latter into two different environments (63, 64), one of which is connected to both of said first and second channel (51, 54) and the other is permanently sealingly separated from said one of said environments (63, 64) and is connected to said seat; wherein said first channel and said seat are coaxial to one another and are arranged on opposite sides of said intersection chamber, wherein said second channel extends along a further axis transversal to the axis of said first channel and of said seat, wherein said membrane shutter is arranged transversally to the axis of said first channel and of said seat and cooperates, by means of said second portion, with the second end of the first channel; wherein said second portion of said membrane shutter faces said selection member on the side opposite the one facing at least one of said second ends (53, 56) of said first and second channel (51, 54); and wherein said selection member is movable inside said seat; characterized in that said membrane shutter and said selection member are arranged on one side of the liquid flow from said heater to said supplying area so as to prevent any pressure drop in the passage through said valve. - a pump for supplying said pressurized liquid into a delivery line; - a supplying area of said beverage connected to said delivery line; - a control valve for controlling the flow of said liquid between said delivery line and said supplying area; and- a heater arranged along said delivery line upstream of said valve and of said supplying area; - a first fluid channel defining one of said paths and having a first end connected to said delivery line and a second opposite end; - a second fluid channel defining the other of said paths and having a first end connected to said supplying area and a second opposite end connected to said second end of the first channel for defining an intersection chamber between said first and second channel (51, 54); and - a seat elongated along an axis, opening into said intersection chamber at its own end and movably engaged by said selection member along said axis between an operating closing configuration, wherein said selection member closes the fluid connection between said first and second channel (51, 54), and an operating opening configuration, wherein said selection member allows the fluid connection between said first and second channel (51, 54);