Manual pump

A manual pump comprising:

• a first tubular member having an upper closed end, a lower open end, and a piston extending through and mounted movably in said first tubular member;
• a second tubular member having an upper open end which is fixed sealingly to said lower open end of said first tubular member, a lower closed end, and a first side wall which interconnects said upper open end and said lower closed end, said first side wall having a first inflow check valve and a first outflow check valve spaced circumferentially from said first inflow check valve, said lower closed end having second inflow and outflow check valves and a first opening;
• a third tubular member having a top open end, a bottom constricted end, a second side wall which interconnects said top open end and said bottom constricted end, and a partition provided adjacent said bottom constricted end, said second side wall having a second opening, and said partition having a third opening, said second side wall further having an external thread that is formed near said top open end, said second tubular member being inserted rotatably into said third tubular member with said first and second side walls, and said lower closed end and said partition in contact with one another, respectively, in a water-tight relationship, said second tubular member being rotatable to a first position, where said first outlet and second inlet check valves are aligned respectively with said second and third openings, a second position, where said first inlet and second outlet check valves are respectively aligned with said second and third openings, and a third position, where said first and third openings are aligned with one another;
• and
• a restraining ring member having an inner face which is formed with an internal thread that engages said external thread of said third tubular member in such a manner that said second tubular member can be prevented from disengaging from said third tubular member but can permit said third tubular member to rotate therein.