A fill valve assembly for controlling liquid flow into a reservoir, the assembly including: an adaptor which has a liquid inlet passage therein, and a valve seating face, a valve apparatus including a valve body (20, 21) having an outlet opening for directing liquid into the reservoir and an inlet opening, wherein the adaptor is configured to be demountably fixed to the valve apparatus at the inlet opening; the valve apparatus further including a pressure-responsive member including a diaphragm received in the valve body (20, 21), and peripherally fixed thereto, between portions of the valve body (20, 21), the portions comprising a cover portion which defines the control chamber and a base portion in which the inlet and outlet openings (40, 5) are formed, the diaphragm being movable in response to variations in a control pressure in the control chamber on a first side of the diaphragm with which the liquid inlet passage communicates, wherein the diaphragm has a second side also in communication with the liquid inlet passage, the diaphragm having a valve surface for sealing against the valve seating face of the adaptor to stop flow of liquid from the inlet passage into the outlet opening, and a float-operated means operatively connected to the valve body (20, 21) for varying the control pressure by venting the control chamber, and biasing means including a compression spring acting on the diaphragm such that liquid pressure acting on the first side of the diaphragm acts together with the compression spring to force the valve surface toward the valve seating face of the adaptor, wherein the valve body (20, 21), diaphragm and compression spring of the valve apparatus are demountable from the adaptor as a unit separate from the valve seating face which remains with the adaptor, characterised in that the valve apparatus includes retaining means for retaining the compression spring and the diaphragm together as a unit, the retaining means including: a retainer for abutting an end of the compression spring, which retains the compression spring between the cover portion of the valve body and the diaphragm; a pin having a first end fixed to the retainer, the pin extending through the compression spring and being received to slide in an aperture in the diaphragm, and a stop for preventing the compression spring from pulling a second end of the pin through the aperture in the diaphragm, wherein the valve apparatus further comprises a latch flange provided on one of the adaptor and the valve body (20, 21) and cooperating latch tabs on the other of adaptor and the valve body (20, 21), the latch flange and a mating one of the latch tabs defining inter-engaging lock surfaces (29a, 29b), the lock surfaces (29a, 29b), being urged toward one another by the compression spring while holding the valve surface against the seating face. an adaptor which has a liquid inlet passage therein, and a valve seating face, a valve apparatus including a valve body (20, 21) having an outlet opening for directing liquid into the reservoir and an inlet opening, wherein the adaptor is configured to be demountably fixed to the valve apparatus at the inlet opening; the valve apparatus further including a pressure-responsive member including a diaphragm received in the valve body (20, 21), and peripherally fixed thereto, between portions of the valve body (20, 21), the portions comprising a cover portion which defines the control chamber and a base portion in which the inlet and outlet openings (40, 5) are formed, the diaphragm being movable in response to variations in a control pressure in the control chamber on a first side of the diaphragm with which the liquid inlet passage communicates, wherein the diaphragm has a second side also in communication with the liquid inlet passage, the diaphragm having a valve surface for sealing against the valve seating face of the adaptor to stop flow of liquid from the inlet passage into the outlet opening, and a float-operated means operatively connected to the valve body (20, 21) for varying the control pressure by venting the control chamber, and biasing means including a compression spring acting on the diaphragm such that liquid pressure acting on the first side of the diaphragm acts together with the compression spring to force the valve surface toward the valve seating face of the adaptor, wherein the valve body (20, 21), diaphragm and compression spring of the valve apparatus are demountable from the adaptor as a unit separate from the valve seating face which remains with the adaptor, characterised in that the valve apparatus includes retaining means for retaining the compression spring and the diaphragm together as a unit, the retaining means including: a retainer for abutting an end of the compression spring, which retains the compression spring between the cover portion of the valve body and the diaphragm; a pin having a first end fixed to the retainer, the pin extending through the compression spring and being received to slide in an aperture in the diaphragm, and a stop for preventing the compression spring from pulling a second end of the pin through the aperture in the diaphragm, wherein the valve apparatus further comprises a latch flange provided on one of the adaptor and the valve body (20, 21) and cooperating latch tabs on the other of adaptor and the valve body (20, 21), the latch flange and a mating one of the latch tabs defining inter-engaging lock surfaces (29a, 29b), the lock surfaces (29a, 29b), being urged toward one another by the compression spring while holding the valve surface against the seating face.