This is a very important component in a vacuum operated chlorinator . The Vacuum regulator is normally closed and opens only under vacuum which is created at the ejector. The up stream of the regulator is under pressure and when there is no vacuum in the down stream then, the regulator closes and does not allow any chlorine gas to flow through. On the down stream side of the regulator, a flow control valve is provided which controls the vacuum to the regulator. When the vacuum is applied to the regulator, then the diaphragm in the regulator pushes the spring loaded spindle to open and allow the chlorine gas to enter the regulator.