Control stop and flushing system

A control stop for connection between a pressurized water source and a flush valve, said control stop comprising:

• a housing defining an elongated flow chamber having a longitudinal axis;
• a valve seat in said flow chamber;
• a valve structure in said flow chamber movable in the direction of said axis relative to said valve seat for controlling flow through said flow chamber and the valve structure includes a valve member, a cup and a diaphragm;
• the valve member having a head portion proximate to the valve seat and a stem portion distal the valve seat;
• the diaphragm being a generally hat shaped flexible diaphragm including a brim portion connected in sealing relation to said housing and including a crown portion enclosing said valve member, said crown portion having a flat circular wall engagable with the valve seat;
• the cup being generally hat shaped, the cup being disposed between the head portion of the valve member and the crown portion of the diaphragm;
• and
• the valve structure including an adjustable stop mechanism in communication with the stem portion of the valve member such that the range of motion of the valve member is limited by the adjustable stop mechanism.