A reverse osmosis water supply system, comprising:
- an inlet conduit for supplying a source of feed water under pressure;
- a reverse osmosis unit coupled to said inlet conduit and including means for separating the feed water into purified water and reject water;
- a control valve having a single internal movable valve member for controlling feed water flow through said inlet conduit to said reverse osmosis unit, said control valve including a valve body having a feed water inlet coupled to said inlet conduit and a feed water outlet coupled to said reverse osmosis unit, and a valve seat between said feed water inlet and outlet;
- a reservoir container having a purified water reservoir and a reject water reservoir separated by a movable barrier;
- means for coupling purified water from said reverse osmosis unit to said purified water reservoir;
- means for coupling reject water from said reverse osmosis unit to said reject water reservoir;
- a dispensing valve including a valve actuator movable between open and closed positions;
- means for coupling said purified water reservoir to said dispensing valve for dispensing of the purified water when said actuator is in the open position;
- said valve member of said control valve including a piston member;
- means for subjecting one side of said piston member to the pressure of the purified water within said purified water reservoir to urge said valve member toward a closed position seated upon said valve seat to prevent feed water flow to said feed water outlet;
- and
- means for subjecting the other side of said piston member to the pressure of reject water within said reject water reservoir to urge said valve member toward an open position retracted from said valve seat to permit feed water flow to said feed water outlet;
- said valve body including a valve passage of a first cross section in communication with said feed water inlet and outlet, and a valve chamber of a second cross section, said second cross section being relatively large in relation to said first cross section, said piston member comprising an elongated one-piece component including a first piston within said valve passage for movement relative to said valve seat to open and close said valve seat, and a second piston within said valve chamber and having a first side subjected to the reject water pressure and a second side subject to the purified water pressure;
- whereby said valve member is displaced to the open position by the combined effects of the pressure of feed water at the feed water inlet and the pressure of the reject water in the reject water reservoir when said actuator is moved to the open position and to maintain said valve member in the open position upon initial movement of said actuator to the closed position until the pressure of the purified water within the purified water reservoir builds sufficiently upon refilling thereof with purified water to offset said combined effects of the feed water pressure and reject water pressure to move said valve member back toward the closed position.