A control valve connected to a first water tank and a second water tank for controlling the water level of said second water tank, said control valve comprising:
- a vertical housing having an upper end, a lower end, a float chamber adjacent to said upper end, a valve chamber adjacent to said lower end, a valve seat support provided between said valve chamber and said float chamber and defining a passage communicating said float chamber and said valve chamber, and a valve seat provided on a bottom portion of said valve seat support and immediately above said valve chamber;
- an inlet conduit extending outwardly from said housing above said valve chamber, said inlet conduit having an inlet connected to said first water tank and an outlet adjacent to and communicated with said valve chamber;
- an outlet conduit extending outwardly from said housing above said valve chamber and opposite to said inlet conduit, said outlet conduit having an inlet adjacent to and communicated with said passage and an outlet connected to said second water tank;
- a controlling means for closing and opening said passage, including a shaft movable vertically and provided in said float chamber, said shaft having a top end extending adjacent to said upper end of said housing and a bottom end extending into said valve chamber passing through said passage, a valve block mounted on said bottom end of said shaft in order to abut against said valve seat so as to close said passage, an upper stop fixed on said shaft adjacent to said top end of said shaft, a lower stop fixed on said shaft between said upper stop and said bottom end of said shaft at a predetermined level, an upper float movably sleeved around said shaft between said upper stop and said lower stop in order to push said shaft upward when said upper float abuts on said upper stop so as to cause said valve block to abut against said valve seat, and a lower float movably sleeved around said shaft between said upper stop and said lower stop and below said upper float in order to push said shaft downward when said lower float abuts on said lower stop so as to move said valve block away from said valve seat;
- means for limiting the downward movement of said upper float and the upward movement of said lower float, said limiting means being mounted on said housing between said upper float and said lower float;
- and
- a holding means mounted on said upper end of said housing, said holding means temporarily holding said upper float against said upper end of said housing in order to keep said valve block in a position which closes said passage when said upper float abuts on said upper stop and pushes said shaft upward, said holding means releasing said upper float away from said upper end of said housing when said lower float abuts on said lower stop and pushes said shaft downward;
- whereby, the water level of said second tank can be always maintained at a controlled lowest level according to said predetermined level of said lower stop.