A control valve for a fluid dispensing device comprises a valve stem, a valve body, a cap and an adjustment mechanism. The elongate valve stem has a flange. The valve body comprises a valve bore in which the elongate valve stem is configured to translate, and a flow path intersecting the valve bore and into which the valve stem penetrates. The cap is joined to the valve body to receive the valve stem such that the flange is positioned between the valve body and the cap. The adjustment mechanism changes a position of the cap with respect to the valve body to vary a distance between the cap and the flange which adjusts the force, and thereby the pressure at which the valve opens.