The Cycle Stop Valve model CSV1A is a pump control valve that automatically adjust pump output to match variable flow requirements. Downstream of the CSV1A pressure remains constant as long as demand is between the upper and lower limits of the valve. The 1" CSV1A handle from 1-25 GPM. 
 
As flow rates vary, the change in pressure causes the valve inside this to modulate closer to or farther away from the valve seat. This enables the pressure downstream of the CSV to remain constant depending on pressure fall off. 
 
When there is no longer any demand on the system, the pressure begins to rise and the valve is pressed against the valve seat. The valve and seat are designed to never be able to completely seal. The non-closing seat is sized to allow flow of approximately 1 gpm on the 1" valve. As this flow continues past the seat, water begins to fill the pressure tank downstream of the CSV. As the pressure tank slowly fills, the system pressure will slowly rise to the pressure switch shut off. (Note: Pressure switch shut-off pressure must always be higher than the constant pressure held by the CSV). 
 
Regardless of tank size, when the tank fills, the pressure downstream of the CSV rises to the pressure switch shut-off point and the pump will be shut off. As flow is again demanded from the system, the pressure tank will empty and the pressure switch will start the pump. 
 
Model CSV1A is dual threaded with 1" female NPT and 1 1/4" male NPT, and is adjustable from 15-150 PSI.  There can be no more than 125 PSI maximum differential pressure across the valve. (Difference in pressure between inlet pressure and outlet pressure). 
 
Note: In multiple pump applications, never share a CSV with multiple pumps. Each pump must have its own valve.